Add scroll height indicators to Flickable

The lines removed set the center point of the throttle axis to one extreme of the joystick range. This causes an offset value when the stick is centered if the joystick does not return exactly zero. This is important for vehicles with reversible throttle, such as ground robots or boats.

Verify was failing due to incorrect READ_MULTI max size

This reverts commit bf31c808.

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

Takes less real estate and flows better and small displays

Even though it’s wrong!

Direct connect to PX4 Flow shows up as generic

Verify is still failing though

Windows OS doesn’t disconnect port when you pull plug on USB. This
caused all sorts of problems with previous logic. New logic handles
this correctly.

- Pervasive change to automatically connect to known board types
- Lots of additional changes along with this:
- More exposure of objects/properties to Qml
- Much restructuring in LinkManager and LinkManager clients