More optimization work. Moved special page init functions to common instead of common_post hook. Allowed paths to cache page metadata on filesystem. Phased out the redundancy in $paths->pages that paired a number with every urlname as foreach loops are allowed now (and have been for some time). Fixed missing includes for several functions. Rewrote str_replace_once to be a lot more efficient.

# Used for testing mod_rewrite.
<IfModule mod_rewrite.c>
RewriteEngine on

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule (.*) install.php?do=modrewrite_test&str=$1
</IfModule>