Create Invitations/Requests categories in buddylist.

Ran grunt test.
I think the above new divs can be simplified something like:
```
+      <div class='roster-panel' hidden?='{{ui.mode!=UI.Mode.GET}}'>
+        <uproxy-roster id='get-roster' class='roster'
+            contacts='{{model.contacts.getAccessContacts}}'>
+        </uproxy-roster>
+      </div>
```

i.e. you don't need to dynamically switch the class, and can just hide the parent div which will effectively hide the uproxy-roster as well