Major rework of the master job cache. This moves the local cache on the master off into a returner (local_cache) and changes everyone to use that interface.
Move the job cleanup into the returner
Move the .p file names into global variables within the module-- so they are in one place
Consolidate job dir into a private function
Merge branch 'job_cache' of github.com:jacksontj/salt into job_cache

Conflicts:
	salt/runners/jobs.py