fixed and refactored addBuild and stopBuild, added and fixed tests
improved scheduler, stopBuildSystem kills running builds, therefore tests are safer
fixed a bug in the scheduler, improved tests, added a test for getBuildQueue
implemented getBuildQueue, passed tests
more "functional" design of the scheduler, added tests for the scheduler model, little refactorings
little refactorings in the scheduler
started to write tests for the scheduler implementation, filled some gaps in the scheduler implementation