Improved testability of HistoryUtils
- Made the HistoryUtils methods non static to improve testability.
- Simplified the downloadFileFromUrl method.
- Removed the hidden constructor.
- Rewritten HistoryUtilsTest.testDownloadDataset unit test without PowerMock.
- Ignore the GalaxyWorkflowEngineTest.testRunWorkflow unit test for now: rewrite without PowerMock later.