Some UI improvements for blocking and unblocking

Add unblock to the router table, so unblocking will work at all.

Block form and unblock form return to subscribers list, not
subscriptions list, by default.

showstream action sends its parameters to block and unblock forms to
better return to the right page.

lib/router.php

@@ -101,7 +101,7 @@ class Router
         $main = array('login', 'logout', 'register', 'subscribe',
                       'unsubscribe', 'confirmaddress', 'recoverpassword',
                       'invite', 'favor', 'disfavor', 'sup',
-                      'block', 'subedit');
+                      'block', 'unblock', 'subedit');
 
         foreach ($main as $a) {
             $m->connect('main/'.$a, array('action' => $a));