Indicators api (#1837)

* [API] Added Indicators API

* [Indicators] Converted Follow Indicator to new Indicators API

* [Indicators] Converted URL Indicator to new Indicators API

* [Indicators] Changes to some legacy indicators for compatibility with new Indicators API

* [Indicators] Addressed code review items from https://github.com/nasa/openmct/pull/1837

* Updated tests for URL Indicator

* Adding Indicator API spec

* Address linting issues

* Switched to direct DOM manipulation rather than template compilation to avoid an unnecessary extra holder element

* Updated documentation to reflect changes to API

* Indicators api styling (#2076)

Updated styling for Indicators

* Update API TOC

* Fix color of items w-mct-example areas of Style Guide

Fixes #1837

* Status class refactoring and cleanups

Fixes #1837
- Significant cleanups and name refactoring to allow more
concise selector definitions, with changes in js, html and scss files;
- Updates in Style Guide > Status page, with some content
reorganization and clarification;

* Corrected out of date API

* de-zeptoed Indicator API test spec

* Remove promise from URLIndicator

* Separated legacy indicators support

* Updated Indicator specs to Jasmine 3

* Fixed checkstyle and lint issues

* Moved legacy indicators support to adapter folder

* Various fixes for Indicators

Fixes #1837
- Added SASS constants for Indicator colors;
- Removed commented code;
- Removed unused indicator classes from _messages.scss
- Fixed missing s-status-on class;

* Significant revisions to Style Guide Indicators content

Fixes #1837
- Better documentation including recommendations;
- Better and more concrete examples;

* Style Guide example tweaks

Fixes #1837

* Refinement to Style Guide Status and Limits content

Fixes #1837
- More detail and clarification on Status and Limits;

* Cleanup code

Fixes #1837
- Remove commented styles;
- Line return refinements;

platform/features/clock/bundle.js

@@ -55,7 +55,6 @@ define([
     timerTemplate,
     legacyRegistry
 ) {
-
     legacyRegistry.register("platform/features/clock", {
         "name": "Clocks/Timers",
         "descriptions": "Domain objects for displaying current & relative times.",
@@ -86,11 +85,6 @@ define([
                         "CLOCK_INDICATOR_FORMAT"
                     ],
                     "priority": "preferred"
-                },
-                {
-                    "implementation": FollowIndicator,
-                    "depends": ["timerService"],
-                    "priority": "fallback"
                 }
             ],
             "services": [
@@ -305,6 +299,10 @@ define([
                     }
                 }
             ],
+            "runs": [{
+                "implementation": FollowIndicator,
+                "depends": ["openmct", "timerService"]
+            }],
             "licenses": [
                 {
                     "name": "moment-duration-format",