MetroCircleButton: Made Border customizable and Disabled state better distinguishable
MetroCircleButton: Made Border customizable and Disabled state better distinguishable

It was very hard to tell if a MetroCircleButtonwas disabled without hovering it, this is fixed now, also the border can now be customized.
ye4241/MahApps.Metro,pfattisc/MahApps.Metro,batzen/MahApps.Metro,Jack109/MahApps.Metro,chuuddo/MahApps.Metro,Evangelink/MahApps.Metro,xxMUROxx/MahApps.Metro,MahApps/MahApps.Metro,psinl/MahApps.Metro,jumulr/MahApps.Metro,p76984275/MahApps.Metro,Danghor/MahApps.Metro