14 Main menu screen setup

Affected classes: TankWarsGame, MainMenuScreen, MainMenuController, MenuButton

Altered screenOrientation from "landscape" to "fullSensor" in the android manifests file

Added libGDX Freetype Gradle dependency to get crisper fonts.

Potential problems:

• Is not adapted to android landscape mode, only portrait
• Screen gets black bars for certain aspect ratios as background image is not positioned optimally
• Updated Gradle, may be collisions

Issue #14 (closed)

Closes #14 (closed)