For daemon command all local users will be exposed as dbus objects
If only one local user exists, all other commands will use that user,
otherwise a user has to be specified.
As Signal Desktop does not allow its users to update the contact names,
it would be nice to be able to update contact names from signal-cli when
the latter is the master device.
The command `setContactName` allow to set the name for the given contact
in the local store. `sendContacts` can then be used to push the updated
contact list on Signal servers.
Closes#228