Add new ability: Symbiosis
Add accurate Mega Evolution message

Needs to be added to the client in the future, in addition to (using
Blastoise as an example):

The opposing Blastoise has Mega Evolved into Mega Blastoise!

- It doesn't mention X/Y for Charizard/Mewtwo
Gastro Acid fails against Stance Change
SmellingSalt now has 70 base power
SmellingSalt is now Smelling Salts
Dazzling Gleam hits all adjacent foes
Merge pull request #443 from TalkTakesTime/master

Dazzling Gleam hits all adjacent foes
Fix learnset compatibility checker
Assumptions about Pokemon that don't have real gen 6 movepools yet
are now made in learnset generator rather than compatibility checker.

This fixes a few problems where a Pokemon was assumed to be
transferred from gen 5 when it wasn't.
Add impersonate command
Merge branch 'master' of github.com:Zarel/Pokemon-Showdown