Remove the separate field settings page

Per @webchick's comment at #552604-48: Adding new fields leads to a confusing "Field settings" form (and independent suggestions of the same idea by Jeff Noyes and James Elliott), it would be useful in Drupal 8 to get rid of the separate field settings edit page in the Field UI. It's a confusing extra step, and it duplicates information already available on the main field editing page.

The code hasn't been written for Drupal 8, but the idea has been proposed, so hopefully that's enough to make it Backports-module-worthy :) Patch is attached.