Issue#42

Concerning #42
Removed the adjustBrightness method in the Look.java class.
I replaced the brightness calculation with libgdx shaders, which are available with Open GL 2.0
The shaders have also the possibility to change the contrast (for a future "ChangeContrastBrick").

Jenkins Testrun:
http://jenkins.catrob.at/job/Catroid-custom-branch-no-emma-test/197/
Ui Package Test (web): (These tests are buggy sometimes)
http://jenkins.catrob.at/job/Catroid-single-UI-package-test/169/console
NewProjectDialogTest#testCreateEmptyProject:
http://jenkins.catrob.at/job/Catroid-single-UI-test/986/console