A true way to make right-aligned GUI.
Reason:
Although there can be align="right" in style prototype, it only works internally. If it is applied to button style, it means the text inside the button will be right-aligned, but not the button.
To make right-aligned GUI with the current API, we need to fix the width of the parent element as well as the width of the element itself, so we can calculate how much to put in its left-padding. But if there is a scrollbar that is not always shown, the parent width will vary and hence this approach of right alignment doesn't work, no mention it is troublesome.
Since you are improving the GUI system in 0.15, I hope there will be a better way to do right alignment.
(After seeing the recent GUI request, I finally remember to make this one. Hopefully it is not too late.)
