[WpfBackend] Implement auto detect drag support.
[WpfBackend] Implement auto detect drag support.

antmicro/xwt,steffenWi/xwt,mminns/xwt,akrisiun/xwt,TheBrainTech/xwt,directhex/xwt,residuum/xwt,mminns/xwt,cra0zy/xwt,sevoku/xwt,hamekoz/xwt,lytico/xwt,iainx/xwt,mono/xwt,hwthomas/xwt