Trajectory - Add time synchronization between trajectories. Split update(...) function into updateDurations(...) and integrate(...) to be able to insert time synchronization in between.

Derivation by Mathieu Bresciani:
https://github.com/Auterion/trajectory_generator

It's confusing and there is a corner case where the result is incorrect:
*= 0 will not set the variable to 0 if it's already NAN.

put flight tasks in separate folder and create a lib for each
goal is to select tasks for targets (e.g. because of flash issue)

Plus some style fixes

The FlightTaskManual... tasks already had their internal
setpoint member variables. I switched them to use the
architecture with setpoint member variables as it was
implemented the commit before. They simplify a lot.

This is necessary to allow more and better unit testing.

Restructuring of generic middleware support files, wrapping of the main ROS calls, skeletons for publishers / subscribers