[PreviewField] adds extra steps to sprite assignment

Issue #372 new
Alex Slavski created an issue

If I have a Sprite field without [PreviewField] I can just drag and drop sprite file from Project field - http://take.ms/aa3IB and it will automatically assign its child element - http://take.ms/Hbcp6 but if I use [PreviewField] for a nice and large image preview it will not accept drag and drop from this element http://take.ms/aa3IB but will require me to either use Select button on the inspector image field or drag the child element http://take.ms/Hbcp6 which is counter intuitive, because without the [PreviewField] that Sprite field was still enhanced by Odin.