iOS: fix for document handlers
iOS: update the form filling dialogs to avoid the keyboard hiding the buttons

Also bring up the keyboard automatically
iOS: protect against crashing when handling accented chars in choice fields

Use conversion assuming ascii as a fallback to assuming utf8. The library
should be converting to utf8 but doesn’t currently.
iOS: don’t allow hiding of the navigation bar when it is other than at the root menu

Seems more natural and avoids cases where tapping doesn’t bring the bar back,
hence trapping the user in one of the submodes.
iOS: remove search-bar-transparency hack

Doesn’t work in iOS 7.1: removes the the whole text view