[EDP] Refactor job manager to support multiple implementations

The job manager at the core of Sahara EDP (Elastic Data Processing) was
originally written to execute and monitor jobs via an Oozie server. However,
the job manager should allow for alternative EDP implementations which
can support new cluster types or new job execution environments.

blueprint edp-refactor-job-manager

Change-Id: I61d5baf9029622a411eccd12fbfe802fc85d63dc
Merge "[EDP] Refactor job manager to support multiple implementations"