Use an integer type to keep integrity of the data coming for the autopilot

Return a position object instead of using various getters.

Add latitude, longitude and altitude parameters to loiter function as this
functionality is required to land safely.

Included changes are required to use the autopilot's version complatible with
mavlink 2

Rather than using manual control and therefore losing benefits of the autopilot,
setTargetCoordinates now uses doReposition but with GPS coordinates 200 meters
further away (2 times default radius) than given coordinates.

Merge subscribeOnly function into runPubsub

Add to published variables an array composed of the yaw angle of the the drone, its airspeed and its climb rate.

Send a position array instead of multiple variables

Lower roll value in manual input to do straighter trajectories

See merge request !4

Fix autocontinue to go straight
Fix angle difference when absolute value is greater than 180

See merge request !3

- use positions provided by the GPS to get an accurate timestamp
- remove telemetry variables