UI++, KerbalData, persistent cabin suit ...

- UI
  * new settings: helmet removal, atmospheric IVA suits, suit assignment
- Personaliser
  * KerbalData class to hold per-Kerbal settings
  * customHeads, customHeads, default* -> gameKerbals, customKerbals
  * cabin IVA suits persist until a Kerbal embarks another cabin
  * removed head/suitMultiplier
  * overhauled experience-based suits settings
  * removed KerbalStats support
  * experience-based suits don't work currently
- TREvaModule
  * changed to respect in-game changes of atmospheric IVA suits setting