Fixed post.url wasn't returning full URL

The new Twig sytnax requires methods to be passed with parenthesis.
Extensions Filesystem Reorganization

Feathers, Modules and Themes now all live under a new directory called "contents".

Uploads directory too.
Updated URLs on Audio Feather.

Cleaned up two methods.
Refactored Random() method.

Added body_class to few methods for CSS styling.
Completely placed recaptcha as a Module.
General code cleanup.
Fixed a potential XSS vulnerability.

Thanks JPCERT for reporting it to us.
Fix Chyrp Twig 'url' tag.
Patched an XSS and SQL vulnerability.

Reported by security researcher Alain Homewood, PwC, NZ.
Merge pull request #219 from xhezairi/3.x

Lots of refactoring and fixes to Chyrp 3.0