Alliance forum fixes part 2

+Added the "Forum" link to the game menu (above Game Rules), player
without an alliance, will be able to access to public forums only
+All players can now open public forums (even without an alliance), post
to them, edit and delete them
+Added the possility to add alliances and players to the "Who can view
this forum" list, the graphic was present but there wasn't the database
and code support (conditions aren't coded yet)
+General fixes

NOTE: To play this version without reinstalling the server, you have to
run this simple query:

ALTER TABLE s1_forum_cat ADD (`display_to_alliances` text,
`display_to_users` text)

var/db/struct.sql

@@ -751,6 +751,8 @@ CREATE TABLE IF NOT EXISTS `%PREFIX%forum_cat` (
   `forum_name` varchar(255) DEFAULT NULL,
   `forum_des` text,
   `forum_area` varchar(255) DEFAULT NULL,
+  `display_to_alliances` text,
+  `display_to_users` text,
   PRIMARY KEY (`id`),
   KEY `alliance-forum_area` (`alliance`,`forum_area`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;