Add documentation to Ephemeris classes

Remove unused "Reference" specification from mod files
Add osirisrex files to gitgnore
Make Ephemeris values into properties

include/openspace/documentation/documentation.h

@@ -285,4 +285,13 @@ using documentation::Documentation;
 
 } // namespace openspace
 
+// Make the overload for std::to_string available for the Offense::Reason for easier
+// error logging
+
+namespace std {
+
+std::string to_string(openspace::documentation::TestResult::Offense::Reason reason);
+
+} // namespace
+
 #endif // __DOCUMENTATION_H__