Added Google Analytic campaign parameters to URLs.
Added arc_twitter_utm preference.
Tweaked UTM URL.
Reformatted the documentation.
Added license.
Added text about UTM parameters to documentation.
Improved arc_twitter fields layout on write tab.
Improved regex for URLs.
Updated the handling of links displayed in the admin interface.
Updated version number to 4.3.0.
Merge branch 'dev'