Issue #1886566 by Wim Leers, sun, effulgentsia, quicksketch: Make WYSIWYG editors available for in-place editing.

Issue #1849752 by effulgentsia, Berdir, jibran, neclimdul: Abstract non-Drupal-specific parts of AnnotatedClassDiscovery into a Drupal\Component base class.

Issue #1874936 by frega, Wim Leers: Pluggable in-place editors (allow modules to define new Create.js PropertyEditor widgets).