Updated Level Select scene to use Karl's custom buttons and to load levels from Game Levels folder.

Added a LevelSelector.cs class and changed the LevelSelectSceneGUITest.unity to use Karl's custom buttons.

(This is possibly a duplicate pull request as I tried to submit it twice on the UAT WiFi and both we're greeted with a network error. Sorry if it is!)

Signed-off-by: Hobo42 <taiteryan@gmail.com>