add "Czar is up to date" button

[GoogleCodeExporter]

From Wei-Hwa: For example, imagine that in the upper-right corner of Czar 
there's a count-up timer, which displays "the last time PC checked to make sure
everyone's status is up-to-date."  When PC checks everyone's status,
they reset that timer.  Maybe we think it's important that we have correct
status every hour, so the time turns red after an hour.

Original issue reported on code.google.com by [email protected] on 25 Jan 2013 at 12:53