Create a Job Manager

[mgermain]

Create a JobManager in the style of the CommandManager that include probably the functionalities of job_generator/job_generator_factory and some stuff from scripts/smart_dispatch.py.

This might be a bigger task than it seems, a lot of changes could be needed.
A possible constructor could be:
(base_path, queue, command_manager, command_params, CLUSTER_NAME)

CLUSTER_NAME could be in the queue or somewhere else ?

There might be a need to change things in the CommandManager, consider #90.