get_suite_name: improve support for rose-stem

Now look for `rose-stem/rose-suite.conf` in current directory.
rose suite-stop: add test battery
rose.suite_control: document auto "-n NAME" logic

Update the command reference for those commands that depend on
`rose.suite_control`. In particular, the logic to determine the suite name in
the absence of `-n NAME` is now documented correctly.
Merge pull request #915 from matthewrmshin/get-suite-name-for-rose-stem

rose.suite_control: improve support for rose-stem suites