* Added a backup test suite. This suite is supposed to entirely drop an ArangoDB _system and restore it into a fresh one. This also includes system collections.
* Added more test cases for backup suite. Now tests several authorization/rights cenarios
* Fixed RestReplication Handlers to restore _user collections Properly.
* Updated Changelog
* Added special handling of _users in Restore for MMFiles as well.
* Added JWT secret for cluster execution of this test, also added JWT secret to shutdown call
- split utility functionality into its own file
- add module loader so we can have modules
- move all testsuites into own files
- remove complicated testcase joining / splitting methods