Implement UGC types and public/private.

[vswarte]

Current implementation of UGC share codes doesn't differentiate between public/private UGC registration nor does it differentiate between emblem or AC. The latter is required for a functional sharing function as this parameter comes back in the GetUGC response. The public/private differentiation as well as the UGC type need to be serialized

The official server generates a random 12 upper-case character alpha-numeric string like F39B4QX8VJ0Z. Private codes use the same string scheme except they're prefixed with @ an example would be @EHP8P9721FWY. This needs to be reflected based on the public/private flag getting sent on UGC registration. I don't immediately recall what field was used for this in the RegisterUGC request, so that needs some investigation.

I am also not sure what field specifies the UGC type on the RegisterUGC call either. Needs discovery.