Veterancy bugfixes

* Units didn't get correct XP when getting more XP than the next level.

* XP points are now transferred when giving units
Cleaned up unit-transfer code when a player dies

* Removed duplicate function TransferUnitsOwnership() in aibrain.lua,
  using SimUtils.lua version instead

* Fixed bug with units not returned to their original owner in Share until death mode.
Updated with veterancy / give bugfixes