Work on #106, allow the broadcast port to be set in the daqdrc.

Update the daq parser to consume a port number as well as a broadcast interface name.

• This introduces a address:port parsing call into the net_writer code to allow it to handle both the port information as well.
• Removes a minor memory leak, by moving from strdup w/o a free to a std::string.
• As we no longer transmit data via daqd data concentrators this removes the DC code path from the net_writer broadcast section.
• Also removes to unneeded constants.