Clarify the title of the "Video Stream" panel (instead of just "Video")

Nope, it's microseconds alright. The autopilot I was testing with indeed only had 19 seconds of "armed" time.

Fix #5812
Show an error message when creating a KML without 2 items at least
Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Converted Structure Scan to use CameraCalc such that it now works with
camera specs.