Always move VoiceOver focus to the current view

Without this, VoiceOver user has to touch-explore to get to the left and right
views. And when top view is restored, they might end up in "nowhere" with
VoiceOver. So post notification to VoiceOver that screen has changed so that
it can reread it and focus the right element.
animated transition between top views
Slider & switch fix (ios5)
fix a typo
fix the top view snapshot frame problem if the app supports landscape mode only
fix the top view stuck before anchor problem when shouldAllowPanningPastAnchor is set to NO
prevent pan gesture from disturbing any vertical scroll view within the top view.