CB-7459 Allow automatic tests to be run for specific plugin(s)

Implementation for https://issues.apache.org/jira/browse/CB-7459

See comments in commits for more details.
I think we should just make this the default.  Ideally when you hit "run auto tests" you are presented with a set of checkboxes, and you hit "go" to make tests run.
Also, it would be nice to use localStorage to remember the set of checkboxes that were previously selected.
Also, it would be nice if the checkboxes went away once you click "go" -- basically the selection screen should be its own "page".
WDYT?