Doxygen warnings generated by code in Ephemeris/ sub-directory fixed Issue #691

git-svn-id: file:///srv/svn/repos/tudat/trunk@528 ac7aa084-b6da-11df-bf42-7fac39f0224f
Doxygen warnings generated by code in MissionSegments/ sub-directory fixed, Issue #696

git-svn-id: file:///srv/svn/repos/tudat/trunk@529 ac7aa084-b6da-11df-bf42-7fac39f0224f
Added Cartesian to spherical state conversions, Issue 674

git-svn-id: file:///srv/svn/repos/tudat/trunk@530 ac7aa084-b6da-11df-bf42-7fac39f0224f