Add correct button types to account settings forms

This is actually a fix in the field_ui base classes so this might have larger-scale implications (in a good way).

Tested, and it works on these URL-s too:
admin/config/people/accounts/display/compact
admin/config/people/accounts/display/full

Suggestions:
1 - remove whitespace:
2229157-primary_button_types_account_forms-2.patch:12: trailing whitespace.
'#button_type' => 'primary',
2229157-primary_button_types_account_forms-2.patch:28: trailing whitespace.
'#type' => 'submit',

2 - We can add primary class to the ajax forms on the manage display pages. I atttach a screenshot about it:

Sure! Fixed the trailing whitespace and added support for the field settings on manage display in the base class. Also updated issue summary.

Looks good!
Please test one more person, and if everything is OK, then go RTBC.

4: 2229157-primary_button_types_account_forms-4.patch queued for re-testing.

I tested it again.
Everything is working.

Very nice! :)

Committed and pushed to 8.x. Thanks!