Bunch of fixes and some additions

Additions:
- recent_posts function, generates an array of the most recent blog posts.
- Display a list of the most recent posts in the Firecrest sidebar.
- Cascade now supports ajax load on more routes.
- Tags are alphabetised on the Write page and when displayed in posts.
- Added relation attributes to prev/next links generator.

Fixes:
- Ajax refresh of comments was broken, now returning valid json response.
- Updated the deprecated and misbehaving `preg_replace` calls in Admin.php.
- h1 elements on error/upgrade/install pages does not wrap nicely - bad line height.