Created class DistanceSwitch and added length() in double precision to PowerScaledCoordinate

include/openspace/rendering/renderable.h

@@ -55,6 +55,7 @@ public:
     static Renderable* createFromDictionary(const ghoul::Dictionary& dictionary);
 
     // constructors & destructor
+	Renderable();
     Renderable(const ghoul::Dictionary& dictionary);
     virtual ~Renderable();
 

include/openspace/util/powerscaledscalar.h

@@ -44,6 +44,7 @@ public:
 
 	const glm::vec2& vec2() const;
 	float lengthf() const;
+	double lengthd() const;
 
 	// operator overloading
 	PowerScaledScalar& operator=(const PowerScaledScalar& rhs);