Add mdk tracker bash completion
Add support for adding and removing labels from an issue
Add basic support for peer review transitions

These will need to be tweaked a bit, but currently offer:
* start peer review; and
* fail peer review.

This change does not incorporate an --end-review, or -pass-review phase.
The end-review should be a meta for comment as per our new PR guideliens
The pass-review should be identical to the fail review, except that it
should transition to "Waiting for integration review" if possible.
Add the ability to leave comments
Add the ability to start/stop development
List available transitions