Required a lot of changes to provide at least a decent attempt at proper
editor teardown control.
Also updates HtmlDescriptionFilter and testing to address issue with bad
child iteration which could lead to missed items.
Renamed editor version from comments to basic as it'll also be used for
item descriptions.
- Updated toolbars to auto-refresh ui if it attempts to update targeting
a DOM element which no longer exists.
- Removed MediaNode dom specific click handling which was causing
selection issues, and did not seem to be needed now.
Re-used existing route and moved tinymce help to its own different
route. Added test to cover.
Added new external-content block to support in editor UI.
