Core/Player: Fix a query that was wrongly deleting items

CHAR_DEL_ITEM_INSTANCE deletes by item guid but in Player::DeleteFromDB the guid being used was player's guid.
That means that if player with guid 100 was deleted, the item with guid 100 would also be deleted. This item could or could not belong to the player.

Closes #8883
Closes #9136

Thanks to @vlad852 for finding the issue
DB/Misc: Fixup quest Hot On The Trail (A:24849 H:24851)
Fix up previous commit.
Core: Fixed some compile warnings
Core: Clean up whitespace, and remove a silly warning in boss_lurker_below.cpp
Core: More clean up whitespace
Core/Accounts: sessionkey field in account table is only a temporary storage to pass data from authserver to worldserver and should only be used as such. Clearing sessionkey from database after a successful login to prevent possible exploits.