Add `Tag` support for `Job`s

[wslulciuc]

We currently support tagging datasets and fields, but we should also expand support to include tagging jobs. For example, we have the job types BATCH , STREAM, SERVICE and some tags could include:

• WEEKLY, DAILY (relates to scheduling)
• SPARK , AIRFLOW (relates runtime execution)

[davidsharp7]

So we would need an additional table to capture the mapping - something like

and a couple of end points

POST http://localhost:5000/api/v1/namespaces/{namespace}/jobs/{job}/tags/{tag}
DELETE http://localhost:5000/api/v1/namespaces/{namespace}/jobs/{job}/tags/{tag}

@wslulciuc - can you think of anything else we might need (excluding UI changes)