Use actual name when importing public key into GPG keyring

When I `keybase track` a user, their public key is automatically added to my GPG keyring. (I _love_ this feature, by the way.) But in the Name field, instead of the full name associated with that account on Keybase, instead I see: "keybase.io/keybase_username". (This might just be with users who created their keys via keybase.io rather than having generated them separately, I'm not sure.)

I don't think it needs to be namespaced this way, does it? I'd rather that had the real name as entered by the user into their account, and the comment field can be used to indicate that keybase.io was the client. (Also, could it use the email address they like/use instead of `username@keybase.io`? I know that's related to #105, but I'd also hope the default would be the actual email address rather than a forwarding account.)

No files, tests, or implementation entry points are identified in the issue. Begin by locating the `keybase track` flow and its GPG keyring import handling, then trace how profile names, comments, and email addresses are selected. Done means imported keys use the user's preferred identity fields while preserving existing tracking behavior and the related email behavior in #105.

Written by the indexing model from the issue text.