Version 0.9.9.2

- Changed CoordSys.setCurrTAI to CoordSys.setCurrDate for self-consistency.
- Changed CoordSys operator== to test isCurrent and updated the unit test accordingly.
- Changed default date of ICRSCoordSys and GalCoordSys from 2000 to 0 (current date).
- Added a unit test for AppGeoCoordSys's cache.
- Added a unit test for coordinate system default constructors.