rose suite-clean --only=GLOBS

New `--only=GLOBS` option to restrict items to be cleaned.
Improve diagnostic.

rose test battery: use number of processors as number of jobs.

I'll mark this as a change to close #914, as I believe this change handles its main use case.
Not sure I like only as the switch name when there can be more than one "only" thing. "this" or "specify" perhaps?