[0171] Added gossip menus for all cooking trainers

* Reverted gossip menus for cooking trainers to what they were in
classic
* Added conditions for cooking trainers to handle this change
In classic and especially prior to patch 2.3, crafting tradeskills
where taught by trainers splitted in several tiers.
Every tier corresponded to one of the four level of a skill
(Apprentice, Journeyman, Expert, Artisan) and trainers can only teach
tiers below their own: Journeyman -> Apprentice, Expert -> Journeyman,
Artisan -> Expert, Master -> Artisan. When player reached the same tier
as a trainer, the gossip of this trainer would change to indicates
where to train for the next tier
Source regarding this change:
http://www.wowwiki.com/Patch_2.3#Profession