Template/stats refactor:
- Stats are now cached and recalculated every clearVolatile (switchout)
- Power Trick, Power Split, Guard Split, Transform, forme changes now
  modify the cached stat value
- This eliminates the need for pokemon.baseSet, so it's been removed
- pokemon.transformInto has been split into transformInto and formeChange
- pokemon.baseBoosts have also been eliminated, boost changes are now
  calculated on-the-fly like stats themselves
- Overall, stat changes should be a lot more like the cartridge games now
- We're also one step closer to finally getting rid of the ModifyPokemon
  event