Increase iteration speed for command bundle development

[kevsmith]

Cog's current install/enable/assign/wait-for-relay-to-download cycle takes forever. We need to figure out how to dramatically shorten that cycle for command bundle developers.

[kevsmith]

Relay's new dev mode switch helps improve the situation but there are more things we can do:

• Decrease template iteration overhead -- Deploying templates to test edits is tedious and slow
• Support update-in-place for config.yaml -- This saves developers from the upgrade and deploy dance when iterating on a bundle