Issue #23 - PowerUp collection

Bug fixed: Player can now collect power ups and gets the according
bonusses.
Issue #23 - Bomb explosion

Bug fixed: The explosion will as of now, not be stopped when a player or
power up is hit, but try to explode in its full range. The player will
however be demolished whilst the power up will remain intact (not sure
if the latter is the goal)
Fixed #23 - Explosion adjustment and modelling

Bug fix: Bombs will now explode each other and power ups.
Modelling fixing: Pivot points are adjusted so spawning of the models
will be more precise.
master merged into Iss23
Merge pull request #25 from Martichoras/Iss23

Iss23 into master
master into issu24