Fixed "Evaquate the Merchant Square" quest

Added script to fix quest creature interaction and text (need also Database fix).
Only one things:
+ // TODO: fix player's spell for use Knocking spell properly without this!!!
+ pPlayer->addSpell(SPELL_CNOCKING, true, false, false, false);
Can be fixed via other ways? i've not founded other.... 
If knoking spell is not active on plyaer he cannot open the quest door.