Fixed gzip output - no longer depends on ob_gzhandler(), uses gzencode() now with a failsafe available if gzencode() is not available. Public function gzip_output() remains unchanged.

Fixed a few places where page metadata cache should have been purged (there may be a few more commits like this)

Merging nighthawk and scribus branches (now that nighthawk isn't panicked anymore)

First stab at cache management backend. Everything seems to have been tested and working so far, but a number of things require a more specialized cache and can't go through the framework (e.g. user ranks which use references to map usernames to user IDs)