Fixes regarding csrf + refactor some parts of AAC (guilds + forum)

Replace $account_logged->getPlayers() with getPlayersList()
$_REQUEST['todo'] -> $_REQUEST['post']
$guild_errors -> $errors

system/templates/forum.new_thread.html.twig

@@ -1,4 +1,4 @@
-<form action="?" method="post">
+<form method="post">
 	{{ csrf() }}
 	<input type="hidden" name="action" value="new_thread" />
 	<input type="hidden" name="section_id" value="{{ section_id }}" />