Add more doxygen comments for FunctionState.
Add more doxygen comments for FunctionState.

seec-team/seec,mheinsen/seec,seec-team/seec,seec-team/seec,mheinsen/seec,seec-team/seec,mheinsen/seec,mheinsen/seec,mheinsen/seec,seec-team/seec