Sahara Cluster and EDP contexts

These contexts will be used to setup Sahara EDP resources before executing
the Job.

The Cluster context will launch a cluster for each tenant.

The EDP context will set up:
* Data Sources for the input and the output
* Job Binaries to run a job from

Note: A refactoring is done to move Sahara contexts under a separate
module.
Note: The contexts do not start any executions.

Change-Id: I8a7420fcc5fc06eaf70a3f1ad4f573a2811ce303
Merge "Sahara Cluster and EDP contexts"