0.5.6 Score and GUI

Score and GUI Implementation
- Galaxy.cs now tracks the player’s current score and displays an
interpolated score when the score is incremented.
- Enemy.cs now has a Score Value field that dictates the base score the
enemy awards when destroyed.
- The Main Camera GameObject now has a child Canvas GameObject that
manages the GUI. It and its child elements are cached in Galaxy.cs.
- The Canvas has a Score text display that displays the current game
score.
- Added RubikMonoOne font for GUI use.