Issue: Special Hooks Slow

The Legacy hooks in VaultWiki slow down page generation considerably (~50 milliseconds). Also, hooks with multiple legacy versions do not function properly.

In vault/special_functions.php, the function special_hook needs to be replaced and function special_hook_assoc added.

In vault/special_plugins_admin.php, the functions special_admin_options_print and special_admin_options_processing need to be replaced.

This will store very slightly more data in memory, but will avoid parsing an XML file during run-time on every wiki page.