Bug 1056877 - Add the UI docs pages to the main table of contents

The UI docs are now being built at the same time as the main service
docs. Until we combine them, let's at least make sure the UI parts are
still discoverable, by adding them to the main table of contents.

docs/index.rst

@@ -19,6 +19,7 @@ Contents:
    common_tasks
    submitting_data
    troubleshooting
+   ui/index
 
 
 Indices and tables

docs/ui/index.rst

@@ -3,8 +3,8 @@
    You can adapt this file completely to your liking, but it should at least
    contain the root `toctree` directive.
 
-Welcome to Treeherder's UI documentation!
-=========================================
+Treeherder's UI
+===============
 
 Contents:
 
@@ -13,11 +13,3 @@ Contents:
 
    installation
    plugin
-
-
-Indices and tables
-==================
-
-* :ref:`genindex`
-* :ref:`modindex`
-* :ref:`search`