Remove unused code from NPC

level is parsed, but isn't used anywhere
stock, vox_intro, vox_quests and dialog are member variables
Merge pull request #1153 from mazayus/fixes

Remove unused code from NPC
Prevent items being equipped to wrong slots when no slot is available

When item ids are the same, we need to make sure that source quantity
+ destination quantity does not exceed the max quantity for that item.
Otherwise, ItemStorage::add() will try to place leftover quantity in the
first empty equipment slot, regardless of type.

Closes #1137
Merge pull request #1154 from dorkster/fixes

Prevent items being equipped to wrong slots when no slot is available
Merge remote-tracking branch 'upstream/master'