Large bundle of fixes and features.

Here's a big bunch of changes I've been working on over the last two months, to make FoF do some things I needed it to do.

Summary of major changes:
+ Database calls are no longer exclusive to MySQL. Currently, only SQLite is additionally implemented, but any other sql datastore won't take much effort to support, now.
+ Added a new sidebar style to choose from.
+ Users may now set a custom sorting-order when viewing items from certain feeds or tags.
+ Added a plugin and preference to make all links from items and feeds open in new windows.
+ Updated much of the emitted HTML for more CSS flexibility, and general modernity.
+ Custom feed titles now work, and are per-user.
+ Addressed some XSS vulnerabilities.