Added dataSourceDelegate
Remove aggregate group members on load
Notify dataSourceDelegate on loading events
Made method -sortNameForRecordID:withSortOrdering:inAddressBook: a class method
Construct KVO keyPath instead of hardcoding string value
Reload tableView when addressBook goes online
Use AKAddressBookDataSourceDelegate to update tableView on reload instead of doing a full reload
Do not hardcode KVO keyPath