Offline Mode?

[davidslater]

Mode that only uses local repos, doesn't attempt to download from s3 (pull git repo), etc. Raises errors if items are not locally available.

This should be an explicit flag that can be set --offline, so that we can ensure in tests that connections are not being attempted.

[shenshaw26]

For right now, I am pulling this back to to-do. We need to get the testing harness completed and then we can re-look at this ticket. Overall, I think the right approach here is to refactor the front end of armory just a bit (aka what is being done here: https://github.com/shenshaw26/armory/pull/6 and then put this ticket in as a part of that effort.