monitoring 7.x-1.0-beta2

Changes since 7.x-1.0-beta1:

• #2538328 by giancarlosotelo, joshi.rohit100: Add max threshold to user registration and comment creation
• #2463769 by Denchev, edurenye, miro_dietiker, Berdir: Backport git sensor improvements: better message, submodule status, branch check and ahead of remote.
• #2532040 by mbovan: Fix disabling sensors using drush
• #2463769 by chaos6522, Berdir, miro_dietiker: Extend sensor: Git: show dirty file in summary message
• #2487035 by othermachines: Fixed Page Not Found in simplytest.me demo
• by Berdir, blueminds: Remove default threshold for info and notice dblog severities.
• #2186725 by ja_ca: Added tests for default theme sensor and disable by default.
• #2227673 by ja_ca: Fixed sensor list not ordered.
• Added explicit test dependency on rest_server and libraries.
• #2271583 by s_leu: Remove wrong exclude condition in past_db sensor.
• #2189261 by blueminds: Fixed ew sensors watchdog log entry every time the Dissappearing sensors sensor runs.
• Remove "irritating text" in non-critical mode from the disappearing sensor settings page.
• #2186981 by miro_dietiker, Berdir: More documentation improvements.
• #2192507 by miro_dietiker: removed unused page callback monitoring/test_service.
• #2186981 by miro_dietiker, Berdir: Clean-up documentation, document runSensor().
• #2187379 by miro_dietiker: Fixed ImageStyleMissing::resultVerbose() still uses removed array argument.
• #2176897 by miro_dietiker: Escape shell commands.
• #2186725 by miro_dietiker, Berdir: New sensor: Default theme.
• #2187065 by miro_dietiker: Log link broken on overview - remove.
• #2161687 by miro_dietiker: Fix {@inheritdoc} use