[WIP] Feature/backends

Done:
 - Changed all instances of protected and private to public (for now)
 - Removed all notions of static

To do:
 - Fix the last test (Resque\WorkerTest::testResumedWorkerPicksUpJobs)
 - Job, Status, Worker etc should all have two very distinct classes; the Model, and the Manager, instead of being mashed together.
 - Rip up the Resque base class and lay it back down.