Add a log server for rebaseline-o-matic.

Just a simple server that accepts updates to the same log entry and shows a simple status page.
Has a special state for the case where there are no NeedsRebaseline lines in TestExpectations
to avoid cluttering the log with useless entries every 30 seconds.

Other than that, new updatelog calls append to the most recent log entry until they have the
newentry parameter, in which case, it starts a new log entry.

Shows the last 3 log entries by default. Not sure what a useful default number is, but that
seems like a good place to start.

Didn't add any tests for the "get" methods since I couldn't wrangle webapp2 unittesting into
submission for methods that call template.render.

Review URL: https://chromiumcodereview.appspot.com/22117002

git-svn-id: svn://svn.chromium.org/blink/trunk@155986 bbb929c8-8fbe-4397-9dbb-9b2b20218538