Make trajectory uploader part of the cflib

[knmcguire]

Currently the high level commander trajectory is partly integrated in the cflib (define_trajectory) and partly defined in examples (uploader class in autonomous_sequence_high_level.py).

It would be great if the trajectory upload class would be part of the cflib that the user only has to call 'upload'

[knmcguire]

There is talk about that the cflib is getting too bulky and that perhaps this should not be part of it. However, @ataffanel argued the trajectory functionality is a functionality that exists within the Crazyflie firmware that usually should be supported fully from the cflib side (even more so than the positioning support).

[whoenig]

I think this should certainly be part of it - all features of the firmware should be usable with cflib. You don't have to include example trajectories, but it should be possible to upload a 2D array with the coefficients (e.g., that one can load from a csv file like done in the Crazyswarm).