prompt1PortMeasure

      prompt1PortMeasure   Prompts the user to measure a reflection coefficient
                           at chosen port (tx)
          G_meas = prompt1PortSOL(vnakit,settings,ports,tx,name)
          input:
              vnakit: (the board) object,
              settings: vnakit settings object, to use existing settings input
                        'current'
              ports: mapping dictionary,
                  possible keys: ['Tx1','Tx2','Rx1A','Rx1B','Rx2A','Rx2B']
                  possible values: [1, 2, 3, 4, 5, 6]
              tx: port number of transmitter
              name: (optional) name of component is printed in the prompt
          output:
              G_meas: [num_pts] measured reflection coefficient over frequency