Add ability to add values to Properties and SystemProperties for D2C messages

[steavy29]

Hi

Right now when you send a message to IotHub, it is only possible to specify message payload. But EventData messages can also contain Properties and SystemProperties.
See https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-messages-construct

I would like to request this feature to be added as sometimes protocols can rely on such properties and without ability to set them it's not possible to use this tool for testing/simulation.

Thanks!