Add scoreboard
Add MouseInputManager & Rectangle
GameScreen uses MouseInputManager

and extends Rectangle
Merge branch 'mouse-input-manager' into score

Conflicts:
	src/screen/GameScreen.java
Extract CircleBoard (new) from GameScreen

GameScreen is responsible for the interaction between CircleBoard and
the Scoreboard and where to draw them.
Merge branch 'master' into score
Scoreboard show how many dots were flushed

Closes #9