* make shouldCancelNavigationBack a var
* rename OWSNavigationView->OWSNavigationChildController
* forward delegate calls to OWSNavigationController
* apply theme and style to OWSNavigationBar consistently
fix themeing on gif picker controller
* Use topPinned navbar position. Size the blur effect view using the background view
* Use fade animation when hiding the navigation bar
* fix issues with reduced transparency setting
* pr feedback
