[Azoth LastSeen] Async statistics loading.
[Azoth LastSeen] Async statistics saving.
[Azoth LastSeen] Bigger saving interval.

60 seconds instead of 3.
[HistoryHolder] Async history saving.
[Azoth Xoox] Check if VCard is the same in EntryBase::SetVCard().

QXmpp from HEAD is required for this.