Unit tests and disabled examples
- ConcatenateExampleTest: added tests for no output and for invalid output.
- RandomLinesExampleTest: added tests for no output and for invalid output.
- GalaxyWorkflowEngineTest: added simple test of the downloadOutputFile method with invalid input (test method: testDownloadOutputFile).
- disabled the RemoveTopAndLeftExample and RnaSeqDgeExample example classes because they are not working yet.