[META][UX] Redesign the "Manage display" form to be consistent with the rest of the admin UI.

[klonos]

I do not currently have the time/energy to word my proposal, but here is a draft of the things I think should get done:

This might not make sense to anybody now, but I promise to come back soon with a proposed mockup ...and a proper issue summary.

[klonos]

...so, the "Custom display settings" fieldset is only shown on the "Default" view mode. To reproduce:

1. go to /admin/structure/types/manage/post/display -> the fieldset is there
2. go to /admin/structure/types/manage/post/display/teaser -> no "Custom display settings" fieldset

Not a bug worth fixing IMO. I have a better UI proposal...

[klonos]

...related: #2250

[klonos]

...how about something like this:

[mikemccaffrey]

This seems like a good change. The current settings are ina non-obvious place.

I think we should try to use the same ui workflow for this that the views ui uses to add/delete additional displays.

[klonos]

Watching the BADCamp training videos, I filed #2305 so that we solve the UX issue with people not understanding that they need to hit the "Save" button on that form. Lets make this a meta-issue and also file separate issues for adding table headers and for making the management of custom displays work more like views (which is an idea I really like @mikemccaffrey 👍 ).

[jenlampton]

I'm going to close this issue in favor of #315 since I believe that will cover these issues as well.