Core/Pets: merged funjoker's new Pet Slot system

* fixed packets and handling for stable master
* fixed Control Pet / Demon handling
* corrected wrong trainer spell for the Control spells
* Added base support for Assist behaivior
* corrected action bar layout
* Hunter Pets will now have the same level as their tamer (patch 4.1 change)
* corrected health stats for pets

src/server/scripts/Spells/spell_hunter.cpp

@@ -1129,6 +1129,9 @@ class spell_hun_tame_beast : public SpellScriptLoader
                 if (!GetExplTargetUnit())
                     return SPELL_FAILED_BAD_IMPLICIT_TARGETS;
 
+                if (!caster->ToPlayer()->GetFirstUnusedActivePetSlot())
+                    return SPELL_FAILED_DONT_REPORT;
+
                 if (Creature* target = GetExplTargetUnit()->ToCreature())
                 {
                     if (target->getLevel() > caster->getLevel())