Distributor modifications

-Moved the persistent store reference from the task executor to the distributor.
-Made the persistent store references in the distributor static to prevent reconnection on every message.
-The distributor now checks the persistent stores instead of queues for running jobs and available simulations.

Signed-off-by: Bennie Leonard <bennie.leonard@gmail.com>
Merge pull request #12 from benniel/distributor

Distributor modifications