Reduce local variable count in planet_add()
Add comment to find_antiscion()
Add comment to find_aspect()
Make gswe_planet_info_free() free its name only if it is set
Remove unnecessary gswe_*_ref() calls

This is to revert part of 41a80ca365c29a435c8d8237e0e8d83128b0809e,
which was kind of an overhead.
Remove unneeded gswe_planet_data_ref() call
Free all objects in gswe_moment_finalize()