Support filters against workflow data in listen task

[fjtirado]

Currently event filter supports filters like

      listen:
        to:
          any:
          - with:
              type: com.fake-hospital.vitals.measurements.temperature
              data: ${ .temperature > 38 }

but it does not support filters that access the workflow data, for example

      listen:
        to:
          any:
          - with:
              type: com.fake-hospital.vitals.measurements.temperature
              data: ${ .temperature > $input.threshold }

[matheusandre1]

Are you doing this? If not, assign the task to me.