Fixed the size of the shield and weapons that destroy the shield now also damages the tank
Powerups and wepaonpickups will no longer spawn in obstacles
Renamned playerList in TankSpawner to playersToSpawn
Corrected fire rate check

timeSinceLastShot should only be updated in update(), not in
fireWeapon()
Fixed the overkill shield thingy where the tank died
Powerups and weaponpickups will no longer spawn inside obstacles
Removed unused code
Removed the images for the old explosion
New icons for the weapons
Added a sound for more events
The volume can now be adjusted with the arrowkeys

This is for testing.
Testing out a new map image
Fixed bug where a tank "died" twice
Finetuned the look of the Lifebar a bit
Merge branch 'dev_images' into dev
Merged with 'dev'