[Edit] Wire in toolbar representer

Wire in representer for handling toolbars in Edit mode,
and add some clarifying documentation. WTD-878.

platform/commonUI/edit/README.md

@@ -31,3 +31,11 @@ proxy in the current selection (in addition to whatever objects the
 user will conceive of as part of the current selection), typically
 with `inclusive` set to `true`.
 
+## Selection
+
+The `selection` property of a view's scope in Edit mode will be
+initialized to an empty array. This array's contents may be modified
+to implicitly change the contents of the toolbar based on the rules
+described above. Care should be taken to modify this array in-place
+instead of shadowing it (as the selection will typically
+be a few scopes up the hierarchy from the view's actual scope.)

platform/commonUI/edit/bundle.json

@@ -94,6 +94,9 @@
             {
                 "implementation": "EditRepresenter.js",
                 "depends": [ "$q", "$log" ]
+            },
+            {
+                "implementation": "representers/EditToolbarRepresenter.js"
             }
         ]
     }