OPC Server Configuration object.
 The object should be placed under the $Node object to configure
 process station as an OPC XML-DA server.

 A Web Service will appear with the URI "http://'nodename':'port'"
 where 'nodname' is the name of the process station, and 'port' the
 portnumber specified in the Port attribute.
 An OPC XML-DA client can request information from this URI, but has
 to be granted access first. Clients that have access to the server are
 specified in the ClientAccess list, with ip-address and accesscode
 for each client.

 Optional description.

 Port for Web Service.

 List with authorized clients.
 Clients are identified by ip-address and given the
 specified access (None, ReadOnly or ReadWrite).

 If the client uses HoldTime and WaitTime for subscription
 request, the opc_server has to be multithreaded.
 'IfNeeded' turns on multithreading if a HoldTime or WaitTime
 is detected.

 Number of currently connected clients.

 Number of served requests.