[Layout] Support sub-object selection in layout (#1811)

Updates to sub object selection, first cut of selection APIs.

* [API] Add inspector view registry to register inspector view providers and show a view in the inspector.

[API] Modify the selection API to register the click event and handle the event. The API will add a class to the selected object and the immediate parent of the selected object.

[Directive] Implemenet mct-selectable directive for making an element selectable.

[Layout] Update the layout controller to use the Selection API. Also, add double click gesture to allow drilling into a selected object.

Populate the Elements pool with contained elements of the selected object. Update toolbar and inspector to listen for the changes in selection.

* [Frontend] Mods to markup and CSS for sub-object selection

* MCTSelectable allows selection in initialization, use to select on navigation

[Frontend] Show grid in first nested layout, hide from deeper nesting. Only show grids when applicable to relative selection.

* Fix checkstyle and lint errors

* Bring back the change that made mct-init-select work

* [Inspector] Make sure the right content is displayed based on whether a view provider exists or not.

* Only show table options when editing

* Make reviewers' requested changes

* Fix broken tests

* [Frontend] Cleanups and tweaks

Fixes #1811
- Cleanups between frame, editor and selecting.scss;
- Hover and selected borders visually pumped up a bit;
- Solid borders on hover and selecting when browsing;
- Dashed borders for layouts when editing;
- Fixed cursor to only show move capability when
element is selected;

* [Frontend] Tweaks to frame.no-frame layout

Fixes #1811
- Margin set to 0;
- Overflow set to hidden;

* [Frontend] Fixed position items border width fixed

Fixes #1811
- Set to 1px;

* Add tests for inspector controller and fix broken tests. Clean up code.

* [Fixed Position] Stop event propagation on click handlers in fixed position to avoid the event reaching the selection click handlers which caused issues with toolbar and selection."

* Fix tests

* Add tests

* Add test

* Remove element from document

platform/commonUI/general/res/sass/user-environ/_selecting.scss

@@ -20,35 +20,51 @@
  * at runtime from the About dialog for additional information.
  *****************************************************************************/
 .s-hover-border {
-    border: 1px dotted transparent;
+    &:hover {
+        border-color: rgba($colorSelectableSelectedPrimary, 0.5) !important;
+    }
 }
 
 .s-status-editing {
-    // Limit to editing mode until we have sub-object selection
+    // Limit to editing mode
+    $o: 0.5;
+    $oHover: 0.8;
+    $bc: $colorSelectableSelectedPrimary;
     .s-hover-border {
         // Show a border by default so user can see object bounds and empty objects
-        border: 1px dotted rgba($colorSelectableSelectedPrimary, 0.3) !important;
+        border-color: rgba($bc, $o) !important;
+        border-style: dotted !important;
+
         &:hover {
-            border-color: rgba($colorSelectableSelectedPrimary, 0.7) !important;
+            border-color: rgba($bc, $oHover) !important;
+        }
+
+        &.t-object-type-layout {
+            border-style: dashed !important;
         }
     }
-
-    .s-selected > .s-hover-border,
-    .s-selected.s-hover-border {
-        // Styles for a selected object. Also used by legacy Fixed Position/Panel objects.
-        border-color: $colorSelectableSelectedPrimary !important;
-        @include boxShdwLarge();
-        // Show edit-corners if you got 'em
-        .edit-corner {
-            display: block;
-            &:hover {
-                background-color: rgba($colorKey, 1);
+    .s-selected {
+        &.s-moveable {
+            &:not(.s-drilled-in) {
+                cursor: move;
             }
         }
     }
+}
 
-    .s-selected > .s-moveable,
-    .s-selected.s-moveable {
-        cursor: move;
+.s-selected > .s-hover-border,
+.s-selected.s-hover-border {
+    // Styles for a selected object. Also used by legacy Fixed Position/Panel objects.
+    border-color: $colorSelectableSelectedPrimary !important;
+    @include boxShdwLarge();
+    // Show edit-corners if you got 'em
+    .edit-corner {
+        display: block;
+        &:hover {
+            background-color: rgba($colorKey, 1);
+        }
     }
-}
+}
+
+
+