CSS tidying, reduce session list h3 font, fix test

Fix the test for active navlinks in front page for /h/, regarding
requiring login.  Fix some CSS indentation.  Add the "/h/" href
back to the navbarlink, to preserve a meaningful statusbar message, but
set the click handler to "return false".
Remove .hangout-offline; add session cap test

Add test to check that only the approved number of heads show up even if
more than the event cap join a session.