Allow authentication username to be specified on remote domain controller definition

At the moment the slave domain controller authenticates against the master domain controller using the name in the host element in the host.xml, as this name is used to uniquely identify the host controller it needs to be unique - this means a user account needs to be created for each host controller.

This task is to additionally allow a user name to be specified on the <remote /> element defining the connection to the remote domain controller - in this case the name specified on the remote element will override the name on the host element - if this name is not specified the existing behaviour will remain.