#311146 by Brian294, dheffron, yched, and others, fix critical javascript problem in new Manage fields UI screen in some themes

#234774 followup - try to preserve selected widget when field type changes, even if widget machine name is different (optionwidgets_buttons vs. nodereference_buttons)

#234774 Nifty new UI to add fields and groups (requires a cache clear) + initial integration with advanced_help module.
Book writers now officially hate me.