UMN Usability: widget option appears twice when adding a field

Just committed a fix for this. More work could be done by adding some jQuery to the process, but the process seems much more intuitive and less confusing.

Rework field and widget type handling to simplify the initial screen when choosing a field and widget type by making it a two-step process where you see only the widgets that apply to the field. Move the setting of the field label to the same place where you set the field name. Change the field edit screen to keep it from showing all the different widgets again and instead just display the current widget. Then add a button to change the widget which will take you to another screen to make the change since the rest of the page will need to change when the widget changes. Keep the changes to the widget label in that separate process, too, since that affects the menu tabs that need to be changed before redirecting back to the main page.

All working well except that changing the widget for an existing field is not redirecting back to the field edit page as it should.