[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/features/layout/res/templates/fixed.html

@@ -40,7 +40,7 @@
             's-selected': controller.selected(element)
          }"
          ng-style="element.style"
-         ng-click="controller.select(element)">
+         ng-click="controller.select(element, $event)">
         <mct-include key="element.template"
                      parameters="{ gridSize: controller.getGridSize() }"
                      ng-model="element">
@@ -53,14 +53,16 @@
              mct-drag-down="controller.moveHandle().startDrag(controller.selected())"
              mct-drag="controller.moveHandle().continueDrag(delta)"
              mct-drag-up="controller.moveHandle().endDrag()"
-             ng-style="controller.selected().style">
+             ng-style="controller.selected().style"
+             ng-click="$event.stopPropagation()">
         </div>
         <div ng-repeat="handle in controller.handles()"
              class="l-fixed-position-item-handle edit-corner"
              ng-style="handle.style()"
              mct-drag-down="handle.startDrag()"
              mct-drag="handle.continueDrag(delta)"
-             mct-drag-up="handle.endDrag()">
+             mct-drag-up="handle.endDrag()"
+             ng-click="$event.stopPropagation()">
         </div>
     </span>