Add better remote control to push-to-trunk auto-roll script.

Add better remote control to push-to-trunk auto-roll script.

This CL enables controlling the automatic push-to-trunk via a settings file .auto-roll in the home directory or via the v8 status app message.

Pushes can be disabled by setting .auto-roll to {"enable_auto_roll": false} or by adding the phrase "nopush" or "no push" to http://v8-status.appspot.com/.

R=ulan@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=18472

[Michael Achenbach, 2013-12-16 11:12:15]

PTAL

[Michael Achenbach, 2014-01-07 10:06:31]

ping

[ulan, 2014-01-07 10:10:37]

lgtm

[Michael Achenbach, 2014-01-07 15:24:04]

Committed patchset #1 manually as r18472 (presubmit successful).