Brief summary of new features from Contao 3.3:
* Add supports of SVG and SVGZ images.
* Responsive images support.
* Specify the order of the internal and external style sheets.
* Additional form field classes.
* Asynchronous JavaScript.
* Image links in TinyMCE.
* Active page in the navigation menu.
* Theme export with SQL files.
* Timing attack prevention.
* Login to comment.
* Skip images without meta data.
* Registration and password mails.
* Insert tag link_name.
* DCA flag "doNotTrim".
* Non-negative natural numbers.
* New hooks and callbacks.
