HereFlow Optical Flow Sensor Testing

@Alberto_Ds,

ok. To be clear though, I never suggested that I would remove support for optical flow. This is what I wrote:

I also don’t think that FlowHold mode works well for most users and I’ve toyed with the idea of removing it.

FlowHold is a mode that relies only on the optical flow sensor and does not require a range finder. This mode does not work well for most users. Other modes like Loiter and PosHold can work quite well with optical flow.