New feature: Auto activation of new users.

Here is a patch which will add in the ability to automatically activate users when they register. You can try the feature by registering here: http://arduino.land/FAQ/ and checking your email.

![Disable/Enable auto activation switch](http://arduino.land/Images/FAQ/Debug/auto-activate.png)
This patch will only show in the config panel for English FAQ's however the feature is still active.

As with my previous pull-request, would copying the English values into the other languages be a solution for now.