Core/BattlePet: Initial implementation of Battle Pets.

 - No Battle Pet trainers yet, use .cast 125610 for the time being.
 - Battle Pets can be added via items, their starting level can be changed in the worldserver.conf.
 - Stat calculations should be correct for all pets but report any errors.
Core/BattlePet: Derp, forgot to remove some test code.
Core/BattlePet: Should fix Linux build and warnings.
DB/Creature: Updated Battle Pet creature entries.
Core/BattlePet: Finished implementing Battle Pet name query.

Fixed releasing/deleting Battle Pets from the journal.
Removed the obsolete 'BattlePetDefines.h'.
A few other misc changes.
Merge branch 'battlepet' of https://github.com/ProjectSkyfire/SkyFire_5xx