0 is legal in most cases except for Gen2 and BDSP!
...it's technically possible to get 0 in BDSP if you have autosave turned on and have an Egg in your party after hatching one before it, but it will hatch immediately on your next game startup, so disallow it anyway.
Yay abstractions to hide away the quirks.
BDSP traded eggs set HT_Friendship and the CurrentHandler flag, but the HatchCounter is always the OT_Friendship value.
Trades always receive BaseFriendship, instead of a hardcoded 50. Necessary to not hardcode because it's immutable for eggs.
Clicking the hatch counter label now sets it to the legal minimum hatch counter (best), and control clicking sets it to the max (worst). Check the encounter template for the true maximum.
