Add more output when `mdm add` fails, to help users as yet unfamiliar with mdm be aware that there is a distinction between source and release repositories.
Add new utility function to allow use of scoped working directories.
Refactor cgw.isRepoRoot to use the new working_directory util, and massage out a new function cgw.getRepoRootPath because I think I'll want that elsewhere momentarily.
Update `mdm status` to use the working_directory util; this also fixes a bug with status not returning the right output when used outside of the repo root.
Fix regression in cgw.isRepoRoot.  Boy, the places you get linebreaks.  Woofdah.
Polish a few places where commands uncermoniously dumped arrays of python strings out; now print them line by line and indented as reasonable instead.
Update README graph to current default topology.

The previously shown graph is still possible, but is not generated by operation in default modes, and modes that produce that topology require better documentation.
Merge branch 'dev'
release version v2.1.2