Cleaned up the inventory handling

Things done:
 - Removed the equips table and added another column which keeps track about
   whether the item is equipped or not
 - Added a message to notify the client about failing equips instead of
   hardcoding to chat notification
 - Removed the move possibillity. It was a quite long function and our future
   idea of the inventory does not need any moves
 - Removed the inInventory and inEquipment parameters from chr_inv_count,
   but added a equipped key to the table that chr_get_inventory returns

This change makes equipped items still being in the inventory. This means
in-inventory triggers are still active! However it makes no sense to disable
this triggers during equipping since it will appear as still in the inventory
to the client.