Add basic Bomb and BombFactory Models
begin bomb detonation logic
Add Bomb Scheduling
Grid to give proper error message if entity not found in grid
Improve SimulationTimer synchronization
Add more Bomb integration tests
Merge remote-tracking branch 'origin/#91-remove-peers-on-disconnect' into #71-bombs
Fix SimulationTimer

timer to no longer require listeners to be re-added after a timer reset
Remove semaphore from BombFactory

BombFactory to use protected counter
Do not stack bombs
Add BombFactory unit test
Bombs to be removed from grid at detonation
Remove all destructible objects in bomb radius

Does not yet properly kill Players
Untested whether objects in radius are actually destroyed
Added power ups
Merge branch 'dev' into #87-powerups
added some comments
Test that bomb destroys objects and kills players
Fix incorrect test
Remove Grid hasPlayer and hasBombAt methods
Merge branch 'dev' into #71-bombs