Add HOOK_TWIG. Also moved Hooks loading to init.php

For adding twig functions & filters by plugins

system/hooks.php

@@ -76,6 +76,7 @@ define('HOOK_GUILDS_AFTER_GUILD_HEADER', ++$i);
 define('HOOK_GUILDS_AFTER_GUILD_INFORMATION', ++$i);
 define('HOOK_GUILDS_AFTER_GUILD_MEMBERS', ++$i);
 define('HOOK_GUILDS_AFTER_INVITED_CHARACTERS', ++$i);
+define('HOOK_TWIG', ++$i);
 
 const HOOK_FIRST = HOOK_STARTUP;
 define('HOOK_LAST', $i);