ModalPane does not interact properly with screenreaders

[crschnick]

When using the Windows screen reader, the contents of a ModalPane are still recognized even though they should not be visible anymore after calling hide().

[mkpaz]

I suppose it’s another JavaFX bug and the screen reader doesn’t take the view order property into account. I’ve checked the list of AccessibleActions and failed to see something suitable.

[crschnick]

Can't you just make it invisible/not managed/not focus traversable when the pane is hidden?

[mkpaz]

Hard to say as it could break the content animations. I would prefer to avoid this level of complexity.

[mkpaz]

Closing in favor of #63 as it's more generic issue.