Be lazy when fetching UserFolder

Since on a lot of requests the routes are loaded (and thus the
application is initialized) it is good to not be greedy. Now we only
fetch the user folder when one of the controllers is actually called.

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

appinfo/application.php

@@ -39,9 +39,11 @@ class Application extends App {
 			return $c->getServer()->getSession();
 		});
 
-		$user = $container->query("UserId");
 		$container->registerParameter("appName", "mail");
-		$container->registerParameter("userFolder", $container->getServer()->getUserFolder($user));
+		$container->registerService("userFolder", function ($c) use ($container) {
+			$user = $container->query("UserId");
+			return $container->getServer()->getUserFolder($user);
+		});
 		$container->registerParameter("testSmtp", $testSmtp);
 		$container->registerParameter("referrer", isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : null);
 		$container->registerParameter("hostname", Util::getServerHostName());