workbench: Add ids to other navbar dropdowns.

This makes them easier to click in integration tests.
workbench: Add basic smoke test.

This visits all the link on a user's front page and makes sure they
all return 200.

It's easy to extend this to crawl the entire site, checking for
success.  I've included the code for that.  We need to squash some
bugs and check the timing before we start doing that, though.

This overlaps api_client_authorizations_test, so I deleted that.
workbench: Document deployment Bundle testing.
workbench: Improve integration test Rails launch.

The previous version was susceptible to a race condition where it
would read the file after Rails created it, but before it actually
wrote a pid to it.  This would cause the rake test task to kill itself
later by running Process.kill('TERM', 0).
workbench: Timeout integration test Rails launch.
Merge branch '2288-smoke-test'