Added support for display name in DataProperty and NavigationProperty

Hi,
I found some hints in the internet (stackoverflow & co) that in order to have the %displayName% replaced in the validation messages with a proper display name, one should set the displayName field in the DataProperty. I thought that this information could be sent from the server anyway, so why not include it in the metadata already. I did this on my test machine and it works pretty well. I was wondering, though, if we could also send custom metadata from server, like field description and watermark. I understand that this is custom code, but it could be very helpful to allow also setting such fields.

Regards,
Ioan