[0744] Fixed UnitClass for almost all creatures

* Fixed UnitClass for creatures when it is known (TBC-DB/UDB)
* Set default UnitClass to warrior for creatures with no mana
[0745] Fixed stats of many creatures

* Fixed min / max HP, min / max mana and some damages for many creatures based on WoW Bestiary
* Fixed min / max level of a few creatures

Signed-off-by: Cala <calaftp@free.fr>
[0746] Marked NPCs with corrected stats as usable by new stats system

* Marked the NPCs fixed by the previous commit as usable by the new stat
system