Assign actions menu added (alt) and six new actions

Changenotes:

Ingame menu added to assign actions to the actionbar.
Actionbar has been extended to ten slots.
Actionbar configuration saves and loads along with the level data.
Dig has been removed and replaced by Disintegrate and Fireball.
Four new block textures added, for a total of five placable blocks.
Jumping has been improved.