0.6.6 Combos

Combos Implemented
- Combo clock displays on the GUI if the combo is greater than 0.
- Combo clock increments with each enemy kill.
- After a given amount of time, the combo clock resets to 0.
- Combo multiplies the score.
- The score text that flies off of enemies has been moved to Galaxy.cs,
and now properly writes the actual score awarded.
- Removed some extraneous debug logs.