env: expose additional environment variables to jobs

[mdonadoni]

The following variables are currently exposed to jobs:

reana-job-controller/reana_job_controller/job_manager.py

Lines 147 to 152 in f4f955c

	def _extend_env_vars(self, env_vars):
	"""Extend environment variables with REANA specific ones."""
	prefix = "REANA"
	env_vars[prefix + "_WORKSPACE"] = self.workflow_workspace
	env_vars[prefix + "_WORKFLOW_UUID"] = str(self.workflow_uuid)
	return env_vars

We should consider adding more, such as REANA_WORKFLOW_NAME.

We should also consider exposing these environment variables to job-controller itself, for example so that they can be read from a Snakemake specification.