allow hostname for Debug Manager

To have remote debugging working with IBM Developer for z Systems (IDz) in more complex network setups it is easier to use the Debug Manager (DBM). The DBM allows all debug related TCP connections being initiated by the client and this way makes it much simpler to handle cases where clients and the mainframe are separated by gateways with network address translation (NAT). Whenever the DBM is in use a debug session on the mainframe will contact the DBM started task which in turn will send the information about this session to the IDz client via the already established z/Explorer connection. Then the client initiates a connection to the DBM and starts the remote debugging. The problem we're facing is that the information that DBM sends to the IDz client contains the IP address of the mainframe (e.g. 10.100.0.34) and not the hostname (e.g. mymainframe.example.com). This IP address is always the address of the network interface the DBM is connected with. We need to have a way to let the IDz client connect to the DBM with a hostname and not with an IP address. That could be achieved by letting the DBM send a hostname (That would be an option to the Debug Manager) or by letting the IDz client ignore the IP address being sent by DBM and using the hostname of the active z/Explorer connection instead (That would be an option to the IDz client).