Add helper function to convert from ICRS to galactic coords

Also includes creating a util file for coordinate conversions

include/openspace/util/coordinateconversion.h

@@ -0,0 +1,44 @@
+/*****************************************************************************************
+ *                                                                                       *
+ * OpenSpace                                                                             *
+ *                                                                                       *
+ * Copyright (c) 2014-2020                                                               *
+ *                                                                                       *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this  *
+ * software and associated documentation files (the "Software"), to deal in the Software *
+ * without restriction, including without limitation the rights to use, copy, modify,    *
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to    *
+ * permit persons to whom the Software is furnished to do so, subject to the following   *
+ * conditions:                                                                           *
+ *                                                                                       *
+ * The above copyright notice and this permission notice shall be included in all copies *
+ * or substantial portions of the Software.                                              *
+ *                                                                                       *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
+ * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
+ * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT    *
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF  *
+ * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE  *
+ * OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                                         *
+ ****************************************************************************************/
+
+#ifndef __OPENSPACE_CORE___COORDINATECONVERSION___H__
+#define __OPENSPACE_CORE___COORDINATECONVERSION___H__
+
+#include <ghoul/glm.h>
+
+namespace openspace {
+
+/**
+* Converts from ICRS coordinates to galactic cartesian coordinates.
+* \param ra Right ascension, given in decimal degrees
+* \param dec Declination, given in decimal degrees
+* \param distance The distance, or radius, to the position given in any unit.
+* \return A position in galactic cartesian coordinates, given in the same unit as the
+* distance parameter.
+*/
+glm::dvec3 icrsToGalacticCartesian(float ra, float dec, double distance);
+
+} // namespace openspace
+
+#endif // __OPENSPACE_CORE___COORDINATECONVERSION___H__