[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/_frame.scss

@@ -23,15 +23,14 @@
     $ohH: $btnFrameH;
     $bc: $colorInteriorBorder;
     &.child-frame.panel {
+        border: 1px solid transparent;
         z-index: 0; // Needed to prevent child-frame controls from showing through when another child-frame is above
         &:not(.no-frame) {
             background: $colorBodyBg;
-            border: 1px solid $bc;
-            &:hover {
-                border-color: lighten($bc, 10%);
-            }
+            border-color: $bc;
         }
     }
+
     .object-browse-bar {
         font-size: 0.75em;
         height: $ohH;
@@ -92,9 +91,9 @@
 
     &.no-frame {
         background: transparent !important;
-        border: none !important;
+        border: none;
         .object-browse-bar .right {
-            $m: 0; // $interiorMarginSm;
+            $m: 0;
             background: rgba(black, 0.3);
             border-radius: $basicCr;
             padding: $interiorMarginSm;
@@ -104,7 +103,7 @@
         }
         &.t-frame-outer > .t-rep-frame {
             &.contents {
-                $m: 2px;
+                $m: 0px;
                 top: $m;
                 right: $m;
                 bottom: $m;
@@ -115,6 +114,7 @@
                     display: none;
                 }
                 > .object-holder.abs {
+                    overflow: hidden;
                     top: 0 !important;
                 }
             }