Offer to update Documentation for 4.2 Stable Implementing schema plugins

The documentation explaining the schema plugins seems to be out of date, particularly the section about configuring views and the editor, which I guess is actually for version 3 (there is a box that says 'deprecated 3.0.0', my original interpretation of that was that the text that followed doesn't apply to v3, but apparently means 'this is for v3 not v4).

I am working on configuring geonetwork to work with a 19115-3 profile and desperately need to understand more about how to configure the views and editor. If one of the team who understands how v4 works (the connections between the Angular directives, xslts, the html, and the metadata xml) could explain it to me, I'd be happy to write some documentation that's relevant to v4.4, which is what I've been trying to use.

Start by reviewing the existing schema plugin documentation, especially the sections on configuring views and the editor. Trace how the Angular directives, XSLTs, HTML, and metadata XML connect for version 4.4, then update the documentation so its version scope and configuration guidance are clear.

Written by the indexing model from the issue text.