Add a new queue manager connect option: use_system_connection_data

It is used when you want to initialise a client connection, but you want
to obtain the `connection_name` and `channel_name` from one of the system
configuration methods. These being: mqclient.ini file, MQSERVER ENV
variable or CCDT.

Sample usage:

````
WMQ::QueueManager.connect(q_mgr_name: "*SOME_Q_MGR", use_system_connection_data: true) do |queue_manager|
  ...
end
````