change operating system for AppVeyor to Windows Server 2012 R2
change operating system for AppVeyor to Windows Server 2012 R2

SamuelMarks/typeframework,SamuelMarks/typeframework,zekelevu/typeframework,3IE/typeframework,SamuelMarks/typeframework,tsframework/ts-framework,zekelevu/typeframework,3IE/typeframework,3IE/typeframework