Segmented Control Selection

I've added the ability to change the font color and shadow treatment for the selected segment of a segmented control.  I need this in order to implement a design in which the selected segment is a much darker color than the non-selected segments (necessitating a change in font color from dark grey to white).  Along the way, I also added the ability to specify a font size without also specifying a font name.  

Please consider this pull request (or something similar) for inclusion in NUI. Thanks!