Bugfixes, non-stock exp. traits, cleanup

- fixed duplication of TR on GameDatabase reload
- fixed toolbar button on database reload
- fixed `CustomKerbals` being ignored
- fixed persistence of cabin suits on the same scene, but persistence across
  scene switches sacrified
- perks are not hard-coded any more, perk suit buttons moved to roster
- code cleanup, refactorisations
DDS loader enabled, skinningQuality

- DDS loader is always built, but disabled unless isDDSLoaderEnabled == true
- skinningQuality option
Reverted DDS loader to TR_DDS

- DDS loader is only compiled if enabled by TR_DDS
- TRReflection colour is (1, 1, 1) by default