Adding commands for managing layouts.

Adding support for wiping out regions and layouts.
Refactored UI layout manager to allow public knowledge of default layout id.
Enhanced test topo for layout hierarchy.

Change-Id: I254fd494175e753f542f12a664618c1a83f72127
diff --git a/cli/src/main/resources/OSGI-INF/blueprint/shell-config.xml b/cli/src/main/resources/OSGI-INF/blueprint/shell-config.xml
index c767289..5e3577e 100644
--- a/cli/src/main/resources/OSGI-INF/blueprint/shell-config.xml
+++ b/cli/src/main/resources/OSGI-INF/blueprint/shell-config.xml
@@ -631,6 +631,19 @@
             </completers>
         </command>
 
+        <!-- UI Layout commands -->
+        <command>
+            <action class="org.onosproject.cli.net.LayoutListCommand"/>
+        </command>
+        <command>
+            <action class="org.onosproject.cli.net.LayoutAddCommand"/>
+        </command>
+        <!--TODO: add this + completers
+        <command>
+            <action class="org.onosproject.cli.net.LayoutRemoveCommand"/>
+        </command>
+        -->
+
         <!--virtual network commands -->
         <command>
             <action class="org.onosproject.cli.net.vnet.TenantListCommand"/>