Missing items (#3125)

* Missing objects styling WIP

- Grabbing prior work from `missing-items` branch;

* Missing objects styling WIP

- Grabbing prior work on hover and missing theme constants from
`missing-items` branch;
- Refined theme constants values;
- Renamed relevant mixins and classes from "isUnknown" to "isMissing";
- Applied new hover and missing/unknown styling to Folder-view grid
items;

* Missing objects styling WIP

- Significant refinements and additions to `is-missing`;
- Normalize object type icons as a markup `*__type-icon` to support
styling and positioning of `is-missing__indicator` as a markup element;
- Application to tree items, l-browse-bar in main view, c-object-label,
grid view;
- Change hover approach in grid-items and tree to use filters;

* Missing objects styling WIP

- Styles added to object-name component in Inspector, markup simplified;
- Styles added to Tabs view;

* Missing objects styling WIP

- Simplified and consolidated `is-missing` approach into
`.c-object-label` class;
- Modded `.c-object-label` class to use flex 1 1 auto, instead of 0 1
auto - be on the outlook for regression problems!;
- TODO: wire up `is-missing` for real and Folder List view;

* Missing objects styling WIP

- Added `is-missing` styling to Folder list view;
- Cleanups, simplification and normalization with tree items in
list-item and list-view.scss;
- Using `c-object-label` now in Folder list view;
- Removed too-broad `<a>` color definition in table.scss;

* Missing objects styling WIP

- `is-missing` added to layout frames, with support for hidden
frames and telemetry views.
- Further styles enhancement;
- Continued added wiring points into markup;

* Missing objects styling WIP

- `is-missing` added to mct-plot;
- Significant improvements for cursor lock indicators in plots;

* Missing objects styling WIP

- Plot legend fixes, added overflow scrolling for collapsed and expanded
 legends;
- Removed conmmented code;

* Wire up 'is-missing'

- Added property checks on domainObject for status 'missing';

* Fix linting issues

* remove carat from eslint package

Co-authored-by: Deep Tailor <deep.j.tailor@nasa.gov>

platform/commonUI/general/res/templates/label.html

@@ -19,7 +19,13 @@
  this source code distribution or the Licensing information page available
  at runtime from the About dialog for additional information.
 -->
-<div class="c-object-label">
-    <div class="c-object-label__type-icon {{type.getCssClass()}}" ng-class="{ 'l-icon-link':location.isLink() }"></div>
+<div class="c-object-label"
+     ng-class="{ 'is-missing': model.status === 'missing' }"
+>
+    <div class="c-object-label__type-icon {{type.getCssClass()}}"
+         ng-class="{ 'l-icon-link':location.isLink() }"
+    >
+        <span class="is-missing__indicator" title="This item is missing"></span>
+    </div>
     <div class='c-object-label__name'>{{model.name}}</div>
 </div>