[TW] Core/Pet: Pet focus

- Save/Load pet focus so it wont get reset when pet is reset for
whatever reason
[TW366] - Core/Player: Implement a generic method to send out item retrieval mails as it seems to be used in multiple places and also send disenchant roll result as a mail if the player's inventory happens to be full
[TW367] - Core/Player: Missing addition to https://github.com/TrueWoW/TrinityCore/commit/258e593fa61e52957b4e831bbdc562d68ac503a9
Merge pull request #64 from gecko32/Patch8

[TW] Core/Pet: Pet focus
Merge branch 'master' of https://github.com/TrueWoW/TrinityCore into ghbb

Conflicts:
	src/server/game/Entities/Player/Player.cpp