Batch setpid

See merge request !4

There are still more changes needed to have full functionality

latitude functions are now y, and longitude functions are now x instead. 
I also recognize that setting an actual lat, lon set point in the future may be useful so I have retained those functions.

It now works on the quadcopter. Messages weren't being processed in protection loop before

- The regression test let to a refactor for the circ buffer

currently one test is failing

Fixed issue with printf() hanging. Removed all printfs(). Don't use them!
Fixed issue with mismatched checksums not getting consumed

Ready to test the responses from quad->backend.
Then create the correct response from backend->frontend and print nicely

Callbacks seem to be working now. Response packet is not sending correctly?

Symlinked commands.c/h from groundstation
Adapted callbacks.h/cb_default
Put callbacks in callbacks.c

Conflicts:
	quad/.gitignore
	quad/sw/modular_quad_pid/.cproject