#38 Ajax interface

[Jeremy Dorn]

Convert most of the admin interface to use the ajax link handler and Widget::generateResponse().

All of the delete, rename, and create methods should use this. Also, edit description should use this. Can also use for switching the current page/element on all the list pages.

For switching pages/elements on the list pages, should look into injecting history so the back button works.

Also, previews should be switched over, but this may be a lot of work.