Fix base power 0
Now it actually means 'don't deal damage' rather than 'deal 0 damage'
this removes the need to specialcase secondaries and status moves, too
Learnset checker is more forgiving for VGC
- if you bring a level 50 pokemon to VGC, it'll be treated as level 100
  for the purposes of checking level-up moves
- we introduce a new flag 'maxForcedLevel' for this