Transition effects separation:

Show/Hide transition effect is now for Visiblity,
ParentShow/ParentHide is now when one of parents (no matter in which generation) is shown or hidden. Supported parents using this attribute are: UiPage, UiModalLayout.

Simpler code for UiPage and UiNavigator.
Merge branch 'master' of https://github.com/ebatiano/Sitana

Conflicts:
	Sitana.Framework/Ui/Views/Containers/UiPage.cs