Implement multi selection (#2351)

* Modify Selection API to support multi-select via shift click.

* Add support for shift + click to add and remove the selection.

* Display message in Location and Properties for multi-select.

* Define applicableSelectedItems for toolbar items. Move toolbar  control definitions to functions.

* Hide positioning inputs if multi-select. Show a 'non-specific' icon when a discrete setting can't be shown in a mixed setting."

* Add toolbar controls in groups per layout item type. Add nonSpecific property to toolbar items to be used by toolbar controls to show non-specific icon.

* Modify toolbar button to react to nonSpecific flag. Get form value by checking value of applicable selected items.

* Support deleting multiple selected objects.

* Do not disable controls when selected items have mixed setting.

* Revert default color to original value.

* Changes to snap-to-grid

* Remove timeout for updating toolbar after mutation. Do not copy toolbar item when iterating the structure.

* Implement move to top and move to bottom for multi-select

* Implement move up and move down for multi-select.

* Markup and CSS changes for mixed settings in toolbar

- Toggle, color-picker buttons;
- TODO: check other themes and sync;

* Mixed settings styling complete

- Refined and synced theme constants;
- Styling for all toolbar components;
- Text size menu handling;
- Inspector messaging;

* Fix selection path

* Mixed settings styling refinements

- Normalized button styling for mixed style context;
- Better theme constant naming;
- Refined swatch styling, better theme constants;

* First cut at getting the bounding rectangle working for multi-select.

* Set pointer-events to none on c-edit-frame to prevent marquee reacting to click events.

* Delete capturing before calling select.

* Remove EditMarquee from ITEM_TYPE_VIEW_MAP

* Pass selected layout items as a prop to edit marquee instead of selection so that x, y, w, h are updated.

* Multi-select c-frame-edit visual fixes

- WIP

* Add complexContent class for a single selected item whose type is subobject-view.

* Move 'c-frame-edit-move' div to layout frame.

* Saving work - multi-move WIP

* Fixes issue with selection happening at end of drag

* Styles fixed for new markup organization

- Marquee, frame styles;
- $editMarqueeBorder style added to theme constants;

* Significant functionality for .c-frame-edit__move element

- Added .is-multi-selected class to .l-layout when > 1 items selected;
- __move element now handles multi-select and complex content (CC)
objects:
-- 0 to 1 items selected, displays as hover bar with grippy on all CC
 objects,
-- > 1 items selected, __move covers all of the frame of all selected CC
items and doesn't allow sub-object selection, and only displays as hover
bar on non-selected CC objects;
- Added better styling for selected objects while editing;
- Code cleanup and consolidation;
- Left translucent green style applied to __move element to temporarily
aid development;
- TODO: fix line drawing object;

* - Fix an issue where shift click did not remove the selected item from the selection after move.
- Modify telemetry and subobject views to emit move and endMove events.
- Clone selectedLayoutItems to get initial positions instead of selection so subsequent moves start from the current position.

* Fix cursor for __move, code comment refinements

* Code cleanup, line view markup changes

- line view markup brought into line with structure in LayoutFrame.vue;

* Implement multi-resize

* Simplify edit marquee code. Revert image and text views' default position to the original values.

* Fix resize for single selection when snap to grid is disabled

* Hide edit marquee if single line is selected, and show c-frame-edit in line-view instead.

* Fix for LineView handles

* Remove snap to grid toggle button and modify the migration script to convert elements with pixel coordinates to grid.

* Fix resizing single line

* Calculate width and height differently for line to position marquee correctly.

* Fix moving single selected line

* Calculate the height and width for line before comparing them with max height and width to correct the marquee position.

* Change the logic for showing frame edit for lines to check for item id.

* Allow multi-move with line in the mix.

* Implement multi-resize when grabbing SW corner.

* Removed temp green tint from __move element

* Fix object undefined error.

* Implement multi-resize for all items except line (take 2).

* Misc UI 7

- CSS selectors to properly display edit marquee, don't show in browse
mode;

* Fix multi-resize for lines.
Make sure line's height and width is minimum 1.

* Disable inspector views when multiple objects are selected.

* Restored layout grid display on sub-layout selection

* Clean up code

* Fixes

- Edit marquee display fixes;

* More code clean up

* SIGNIFICANT fixes and rewriting in LayoutFrame.vue

- Styles for .c-frame-edit__move element for selection and hovering;
- local controls;
- view large button;
- Theme constants updated;

* Get selected item's index from layoutItems.

* Address review feedback.

* Merge topic-core-refactor

* Reset keyString to empty string after setting original path when domainObject is undefined.
Add proper check for selection.

src/plugins/displayLayout/components/BoxView.vue

@@ -23,7 +23,8 @@
 <template>
     <layout-frame :item="item"
                   :grid-size="gridSize"
-                  @endDrag="(item, updates) => $emit('endDrag', item, updates)">
+                  @move="(gridDelta) => $emit('move', gridDelta)"
+                  @endMove="() => $emit('endMove')">
         <div class="c-box-view"
              :style="style">
         </div>
@@ -54,8 +55,7 @@
                 x: 1,
                 y: 1,
                 width: 10, 
-                height: 5,
-                useGrid: true
+                height: 5
             };
         },
         inject: ['openmct'],