fixed Problem with project in Settings

 - project now gets also deleted from settings
 - added tests
 - refactored testDeleteSprite and testDeleteViaActionBar
 - some minor changes

Jira:
https://jira.catrob.at/browse/CAT-1174

master testrun (8 fails):
https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-Multi-Job-Custom-Branch/2505/#showFailuresLink

refactor_deleteProject testrun (incoming):
https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-Multi-Job-Custom-Branch/2506/

Here you can see that the same test fail also on the master branch:
https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-CustomEmulator-Single-ClassAndPackage-Test/103/
https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-CustomEmulator-Single-ClassAndPackage-Test/102/

https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-CustomEmulator-Single-ClassAndPackage-Test/101/
https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-CustomEmulator-Single-ClassAndPackage-Test/100/

https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-CustomEmulator-Single-ClassAndPackage-Test/99/
https://jenkins.catrob.at/view/All-Categories/view/Catroid/job/Catroid-CustomEmulator-Single-ClassAndPackage-Test/98/