Make Roster entries Map from BareJid to RosterEntry, since only
bare JIDs are allowed as roster items as per RFC 6121 § 3.1.1
When a user sends a presence subscription request to a potential
instant messaging and presence contact, the value of the 'to'
attribute MUST be a bare JID <contact@domainpart> rather than a full
JID <contact@domainpart/resourcepart>,…
Also some further Roster API changes regarding JIDs.