Support reversing visible children

[hillelcoren]

Currently I believe it's only possible to layout the children from left to right (or top to bottom). It would be helpful to be able to reverse this so the children are laid out right to left (or bottom to top) in the available space.

To explain our use case... we're using the widget to show save/cancel/email actions at the top of the screen. We'd like to ensure the save button is always shown in the top right corner and extra buttons are displayed to the left.

Thanks for the excellent package!

[ekuleshov]

I have a similar need. It would be cool to have something like align option, so we could align the child widgets to the right.