SPICE-time dependency, retrieval of spice ephemerides and rotational matrix + coordinate references.

Added functionality:
- New class renderablesphericalgrid is repurposed code from powerscaledsphere class.
  Due to z-buffer issues used as reference grid to confirm planetary orbits are correct.
  This has been a major problem as prior we had no visual reference.
  Now we have a Galactic-, Celestial- and Ecliptic-coordinate grid.
  To this also added separate shader: grid_vs.glsl / grid_fs.glsl
  These grids have a static-rotational matrix derived from partiview (thanks to Brian)
  since spice req. to-from frame to compute rotational matrix.

Time dependency:
- Added struct RuntimeData - which for now only contains openspace time and is passed to all renderables
- All renderables accept runtimeData, keep private reference and use for computation of rotational matrix
- This obviously carries corresponding changes to Scenegraph and ScenegraphNode.

Spicemanager:
- Added function that more easily provides access to rotational matrix used in spice
 (used in renderableplanet for computing planetary objects spin around axis)

Ephemeris-classes:
- Now compute ephemeris from spice based on timeepoch in runtimedata
  TODO: once z-buffer fixed - set ephemeris correctly as meters (not kilometers)

Renderengine:
- Advances time with the advanceTime method in RuntimeData struct

ISSUES:
- Our Y axis NOT same as SPICE or star-catalogue, all renderables rotated now 90deg, needs redefinition,
  lots of debugging and major headaches before this conclusion.
- Depth buffer needs to be fixed in order to properly place planets.
- Spice kernels have finite time-range, when time stops - simulation ends - ugly fix: reset time to zero.
  Possible fix: kernels de431 (part 1-2) cover huge timespan and most likely have functions to extrapolate time,
  drawback is that they are 1,7 gb each.

TODO:
- Compute and draw dynamic ephemeries for each renderable. Either do full year sweep then update for each point or
  create a tail of linesegments for each planet. Dont know yet how to do this, would like spicephemeris to be
  sub-class of Renderable (have own render() method) - good/bad?

include/openspace/util/constants.h

@@ -68,7 +68,12 @@ namespace planetgeometry {
     const std::string keyType = "Type";
 } // namespace planetgeometry
 
-
+namespace renderablesphericalgrid{
+	const std::string gridType = "GridType";
+	const std::string gridColor = "GridColor";
+	const std::string gridMatrix = "GridMatrix";
+	const std::string gridSegments = "GridSegments";
+}
 
 namespace ephemeris {
     const std::string keyType = "Type";

include/openspace/util/runtimedata.h

@@ -0,0 +1,39 @@
+#ifndef __RUNTIMEDATA_H__
+#define __RUNTIMEDATA_H__
+
+enum increment{
+	YEAR, MONTH, DAY, HOUR, MINUTE, SECOND, MILLISECOND
+};
+
+struct RuntimeData{
+public:
+	RuntimeData() :_openspaceTime(0.0){
+	};
+	void   setTime(double time) { _openspaceTime = time; }
+	double getTime() { return _openspaceTime; }
+
+	// cant come up with proper user friendly-method, this will do. 
+	void advanceTimeBy(double nr, increment incr){
+		switch (incr){
+			case YEAR:        _openspaceTime += (nr * year);     break;
+			case MONTH:       _openspaceTime += (nr * month);    break;
+			case DAY:         _openspaceTime += (nr * day);      break;
+			case HOUR:        _openspaceTime += (nr * hour);     break;
+			case MINUTE:      _openspaceTime += (nr * minute);   break;
+			case MILLISECOND: _openspaceTime += (nr * millisec); break;
+			default :         _openspaceTime += (nr);
+		}
+	}
+
+private:
+	double _openspaceTime;
+
+	double year     = 3.154*pow(10, 7);
+	double month    = 2.628*pow(10, 6);
+	double day      = 86400;
+	double hour     = 3600;
+	double minute   = 60;
+	double millisec = 0.001;
+};
+
+#endif // __RUNTIMEDATA_H__

include/openspace/util/spicemanager.h

@@ -28,6 +28,7 @@
 
 #include <string>
 #include <ghoul/glm.h>
+#include <glm/gtc/type_ptr.hpp>
 #include <vector>
 #include <map>
 
@@ -44,7 +45,7 @@ public:
 	static SpiceManager& ref();
 	
 	/**
-	 *  Load on or more SPICE kernels into a program. If client provides
+	 *  Load one or more SPICE kernels into a program. If client provides
 	 *  the path to a binary kernel or meta-kernel upon which its loaded 
 	 *  to the appropriate SPICE subsystem. if the file is a textkernel 
 	 *  it will be loaded into kernel pool. 
@@ -110,6 +111,7 @@ public:
 
 // Converting between UTC and Ephemeris Time (LSK)  ------------------------------------- //
 
+
 	/**
 	 *  Convert a string representing an epoch to a double precision
      *  value representing the number of TDB seconds past the J2000
@@ -121,6 +123,8 @@ public:
 	 */
 	double stringToEphemerisTime(const std::string& epochString) const;
 
+	std::string ephemerisTimeToString(const double et) const;
+
 // Computing Positions of Spacecraft and Natural Bodies(SPK) ---------------------------- //
 
 	/**
@@ -144,7 +148,7 @@ public:
 						   const std::string& aberrationCorrection,
 						   const std::string& observer,
 						   glm::dvec3& targetPosition, 
-						   double lightTime) const;
+						   double& lightTime) const;
 	/**
 	 *  Return the state (position and velocity) of a target body 
      *  relative to an observing body, optionally corrected for light 
@@ -168,7 +172,7 @@ public:
 						const std::string& observer,
 						glm::dvec3& targetPosition, 
 						glm::dvec3& targetVelocity,
-						double lightTime) const;
+						double& lightTime) const;
 
 // Computing Transformations Between Frames (FK) -------------------------------------- //
 
@@ -203,6 +207,12 @@ public:
 		                            const std::string& toFrame,
 		                            double ephemerisTime, 
 									transformMatrix& positionMatrix) const;
+
+
+	void getPositionTransformMatrixGLM(const std::string& fromFrame,
+									   const std::string& toFrame,
+									   double ephemerisTime,
+									   glm::dmat3& positionMatrix) const;
 	
 // Retrieving Instrument Parameters (IK)  ------------------------------------------ //
 
@@ -351,8 +361,8 @@ private:
 * or <code>getPositionTransformMatrix</code> the instantiated object
 * can transform position and velocity to any specified reference frame. 
 *
-* Client-sied example: 
-* openspace::transformMatrix m(6);
+* Client-side example: 
+* openspace::transformMatrix stateMatrix(6);
 * openspace::SpiceManager::ref().getStateTransformMatrix("J2000",
 *                                                        "IAU_PHOEBE",
 *                                                         et,
@@ -367,16 +377,17 @@ private:
 	int N;
 	double *data;
 	bool empty;
+
+	friend class SpiceManager;
+public:
 	double* ptr()   {
 		empty = false;
 		return data;
 	}
-	friend class SpiceManager;
-public:
 	/* default constructor */
 	transformMatrix();
 	/* default destructor */
-	~transformMatrix(){ delete[] data; };
+//	~transformMatrix(){ delete[] data; };
 	/* allocation of memory */
 	transformMatrix(int n) : N(n){
 		data = new double[N*N];

include/openspace/util/time.h

@@ -14,6 +14,7 @@ public:
 	static bool isInitialized();
 
 	void setTime(const char* stringTime);
+	void setTime(double intTime);
 	double getTime();
 
 private: