Support ExtensionDictionary also for AutodeskProperties, in addition to XData

Currently what we have for Entity.AutodeskProperties is actually XData (https://adndevblog.typepad.com/autocad/2012/04/using-net-api-to-add-and-remove-xdata-.html), but XData is a legacy mechanism (https://www.keanw.com/2007/04/adding_xdata_to.html), ExtensionDictionary is the way to go!

So I hope you can support it also.