Improve keybase.io support

This removes the hack of storing the keybase id as user id, makes searching for 0x* keys work, puts best matches on top, reduces bandwidth usage, displays the match's github and twitter accounts and the first website, also cleans up a little.

It also removes username@keybase.io, as that suggests it is a valid email address to reach the user, which isn't the case. keybase.io/username has been used instead.