bring back user page

Adds a UserView that contains a MainSplit with an empty div
and a RightPanel, preset to the given member.

UserView fetches the profile and creates a fake member, which
it passed on to the RightPanel.

this doesn't use the view_user action on purpose, to avoid any
interference of the UserView when trying to view a room member.

res/css/structures/_MainSplit.scss

@@ -0,0 +1,21 @@
+/*
+Copyright 2015, 2016 OpenMarket Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+.mx_MainSplit {
+    display: flex;
+    flex-direction: row;
+    min-width: 0;
+}