#107 time mocking

Fixes #107 

Enables time "compression" on SimulationTimer, and  eliminates the vast majority of waiting time for the Bomb and Powerup tests.

To eliminate waiting time in tests, use the static "setTimeMultiplier" to multiply all time updates from the timer.
Assuming all time-bound operations use the time from the SimulationTimer, they will finish faster.

@melari, this isn't exactly what you asked for, but it works quite well!