Added level controller script, to make timed levels
Added restart button to LevelController.
Changed layer collision matrix so that enemies won't destroy obstacles with lasers.
Added a simple GUIManager class so that GUILayout can be more easily used to display information.
Added meteors of all different sizes.
Fixed new meteor objects by setting gravity scale to 0. Moved where the velocity of the objects is set to its own script.
Merge pull request #7 from krytaxion/master

Changes during Game Jam #2