Merge pull request #845 from stfnsche/master

fix error that occurs when openengsb is shutdown
[OPENENGSB-3648] Fixed a lot of checkstyle errors
[OPENENGSB-3648] Added correct license headers and adapted the tests accordingly
Merge pull request #849 from Arcticwolf/OPENENGSB-3648

[OPENENGSB-3648] Make pre-push script runnable again
added missing license headers and a System.out.println call
[OPENENGSB-2793] use newer openjpa maven plugin
[OPENENGSB-2058] Refactored some integration tests so that every test in the class can be run without a new openengsb start
Merge pull request #850 from Arcticwolf/OPENENGSB-2793

[OPENENGSB-2793] use newer openjpa maven plugin
[OPENENGSB-2058] removed some commented code
Merge pull request #851 from Arcticwolf/OPENENGSB-2058

[OPENENGSB-2058] Refactored some integration tests
[OPENENGSB-3631] added functionality to query for commits by their revision number
[OPENENGSB-3631] added revert functionality, added first two tests
[OPENENGSB-3631] added additional tests which show the current problem
[OPENENGSB-3631] implemented the commit revert functionality
[OPENENGSB-3631] reimplemented JPACommit behaviour in order to work finally full correctly
[OPENENGSB-3631] removed no longer needed oid list in the JPACommit entity
[OPENENGSB-3631] Added method to the EDB which allows the querying for commits with the help of the new class CommitQueryRequest, which defines the used conditionals for the query
[OPENENGSB-3631] added functionality to query for revisions to the QueryInterface
[OPENENGSB-3631] started implementing the method for loading an EKBCommit based on its revision number
[OPENENGSB-3631] implemented the loading of EKBCommit objects