Sprite depth and graphics update

Game update to version: dev - 2.0.3

Sprite depth was implemented and added to the game. Bellow you can see an example:


Example

Other changes:
[*] create and add tiles for the other side of a roof
[*] change tree assets
[*] make buff icon smaller in the hud
[*] implement persistence for player owned spells (ability IDs)
[*] display user friendly message when item can not be equipped
[*] fix bug where item on position [0,0] could not have been picked up due to that point being a default value