Task #9893:  MomQueryService now returns strings instead of DateTimes for minStartime and  maxEndTime

Task #11020: Added docstrings to schedulers and fixed a problem with instantiating  the DwellScheduler.

Task #10780: Added unit test to cover some more pushing back start/end times situations. Test coverage 92%

Task #10948: Renamed assigment.py to resource_assigner.py, and revived unit tests for ResourceAvailabilityChecker (one test still requires discussion, see TODO). Currently working on unit tests for ResourceAssigner itself.

Task #10780: Fixed use case where task start_time > now and  end_time < start_time resulted in an failing RPC to RADBService. InsertSpecificationAndTask()  - failing since RADB doesn't allow for end_time < start_time. New behavior is in these cases to change end_time to end_time = start_time + 1 hour

Task #10780: Refactored ResourceAssigner such that it uses the new DwellScheduler (instead of resource_availability_checker.get_is_claimable()), refactored ResourceAvailabilityChecker such that it can be injected into the schedulers. The latter is still a work in progress: refer to the TODOs in these files for more information.

Task #10780: ResourceAvailabilityChecker and ResourceAssigner and their unit tests are separated now, and fully PASS

Task #10780: Done refactoring ResourceAssigner, ResourseAvailabilityChecker still to refactor and move to separate file

Task #10780: Started refactoring doAssignment() up until the call to the findclaims() function. Refactored unit tests accordingly.

Task #9939: assigner, RAtoOTDB propagator: address Auke's review comments + a few small cleanups of my own

Task #10801: Fixed indentations, added test for invalid root_resource_group, fixed test for RCUs, fixed duplicate test names