Add functionality to transfer anchor position from the Crazyflie to a client

[krichardsson]

Implement some sort of transportation of anchor position data from the CF to a client over CRTP.

Currently the anchor position is set in the Crazyflie from a client using the parameter sub system. The positioning system is under redesign and anchor positions will be stored in the anchors instead, to support this we need a way to transfer anchor position data from the copter to a client. Primary candidates for this is to use the memory- or logging sub systems.