Convert the resource manager to use the database for state.

Also, add the beginnings of a babysit Task.
Converted a few more tests to use the databased backed resource manager.
Fix the remaining tests so that the database backed resource manager's tests all pass.
Merge branch 'distributed-tasks' into rbarlow-babysitter

Conflicts:
	server/pulp/server/async/tasks.py
	server/test/unit/server/async/test_tasks.py
Added tests for the babysit() function.
Added unit tests for the models in pulp.server.db.model.resources.
Added several tests for the pulp.server.managers.resources module.
Update the DISTRIBUTED_TASKS_README.txt for the changes made in this branch.
Added a note about Celery Beat to the README.
Remove id and _id from the ReservedResource Model correctly.
Fix a comment that references the ResourceManager.
Remove more references to the ResourceManager.
Added a :return: section to a docblock.
Used the © symbol instead of (c).
Merge branch 'rbarlow-babysitter' into distributed-tasks