Drone2 DRONE-2

Refactoring
 - introduced DroneBrick as base type
 - renamed Drone stage members & adopted tests

Issue: 
https://jira.catrob.at/browse/DRONE-2?jql=project%20%3D%20DRONE

Testrun:
https://jenkins.catrob.at/view/All-Categories/view/Catroid-multi-job/job/Catroid-Multi-Job-Custom-Branch/1587/