Use a title callback instead of drupal_set_title()

http://drupal.org/commitlog/commit/28254/431a6e7706a4f13cd52cfecb98d64da... is definitely a step in the right direction. We don't want drupal_set_title() inside form builders.

However, it'd be even nicer if fape_field_edit_page() didn't call drupal_set_title() at all, but instead used a 'title callback' on the menu item. That'd make it even easier to embed the output of this into custom ctools content_type plugins to use on panels pages without clobbering the title.

That said, you'd have to duplicate a fair bit of the work from the title callback and the menu item callback itself to get enough data to compose the right title. That's obviously why it's there already. Same story with the access callback. So, this probably isn't a trivial issue. Probably we need some shared helper function (perhaps with a static cache for some of that junk) so that it can be easily reused between the title callback and menu callback...