Custom slide animations need fragment reordering

[thirteenthstep]

In its current implementation, ScreenStack will reorder fragments only in case of SLIDE_FROM_BOTTOM oder FADE_FROM_BOTTOM animations.
This behavior prevents some custom slide animations, since these will often also need the fragments reorderd, e.g. if the underlying screen ist not moved by 100% oder not moved at all.

I would suggest to add those slide animations as case in needsDrawReordering:

private fun needsDrawReordering(fragment: ScreenStackFragment): Boolean =
            when (fragment.screen.stackAnimation) {
                StackAnimation.SLIDE_FROM_BOTTOM, 
                StackAnimation.FADE_FROM_BOTTOM, 
                StackAnimation.SLIDE_FROM_LEFT, 
                StackAnimation.SLIDE_FROM_RIGHT -> true
                else -> false
            }        

It might even be an option to reorder fragments by default, since it seems only natural that the entering screen should be on top.