Fix stylesheet loaded from wrong location

Fix stylesheet path not taking into account the web_root config.

views/head.ejs

@@ -1,5 +1,5 @@
 <title>Clusterio</title>
-<link rel="stylesheet" type="text/css" href="/style.css">
+<link rel="stylesheet" type="text/css" href="<%= locals.root %>style.css">
 <script>root = "<%= locals.root %>";</script>
 <script src="<%= locals.root %>external/jquery.js"></script>
 <script src="<%= locals.root %>external/jquery-ui.js"></script>