Fixing #597 and cleaning up admin/inc/functions_themes.php in terms of docblocks and variable/array initialising.
Re-caching stylesheets on upgrade for 1.8 to ensure existing stylesheets get minified.
Merge branch 'feature' of https://github.com/mybb/mybb into fix-597

Conflicts:
	install/resources/upgrade30.php
Added task to re-cache stylesheets via ACP without having to manually go into each style and save it.
Merge pull request #785 from euantorano/fix-597

Fixing #597 and cleaning up admin/inc/functions_themes.php in terms of d...