Issue with increaseAtPos

[dabates]

Reference #82

Fixes around what TEMP returns.

Talked to @Brightrim about this issue, changed the function

• Returns the new "amount"
• Adds the update to the world so the display updates immediately

[vilarion]

This is not documented correctly. increaseAtPos returns not the new number, but the number of items it was unable to create in the given slot. That being said, I am up for changing this behaviour.

• The same change would have to be made in Character::increaseAtPos for consistency.
• The same change would have to be made in Player::increaseAtPos for consitency and also clean up code duplication.
• The server uses this function as well, make sure the slot update is not sent to the client twice.