Add css changes from MIT's local media files

While cleaning up MIT's media setup, @luac and I found local changes to onsite_ajax_status.css, which seem like they would be useful to other chapters.  In particular, make the third block of settings at the top have a scrollbar, and make some of the text more readably-sized.  We didn't write these, though, so we don't really know if they're all necessary or desired, but we wanted to get them into git.

(cherry picked from commit 6404d0c0b2daf738f3339de13f90f031750291e6 in mit-prod)