Folder metadata

Added web client folder metadata support (issue #101).  The metadata is shown below the contents list and reuses all of the metadata code for items.  As part of this, I converted the internal 'item-metadata' references to 'widget-metadata' to make the naming more reasonable.

I fixed the unicode issue with metadata (issue #422), by generically not sending objects in the model save method.  I added a test to verify this.

I disliked how dialogs would slide in and then the values would populate, so I changed that.  I think I'll have to update the edit assetstore dialog to do the same once that gets merged in.
Looks like the third argument `obj` is unused.