Adds manager actions to allow move/remove/forward individual messages

Adds manager actions to allow move/remove/forward individual messages
in a particular mailbox folder. The forward command can be used
to copy a message within a mailbox or to another mailbox. Also adds
a VoicemailBoxSummarry, required to retrieve message ID's.

Resolves: #181

UserNote: The following manager actions have been added

VoicemailBoxSummary - Generate message list for a given mailbox

VoicemailRemove - Remove a message from a mailbox folder

VoicemailMove - Move a message from one folder to another within a mailbox

VoicemailForward - Copy a message from one folder in one mailbox
to another folder in another or the same mailbox.