Prep for combining the Nidoran and Volbeat/Illumise families.
This isn't strictly necessary, but it makes sense for the evolution
tables to be "Pokemon"-prefixed since, hey, evolution is a Pokemon
thing.
There are now (well, have been for a while) multiple ways to evolve
a Pokémon from its unique parent, so the current schema wasn't working.
The parent Pokémon has moved back to the main pokemon table, and
pokemon_evolution has grown an artificial primary key.
New evolution methods for Milotic, Leafeon, Glaceon, Magnezone, and
Probopass have been added.
