flex, gsr, emg, etc - averaging over noisy samples missing or not implemented in C

[jontrulson]

These drivers are noisy, and rely on averaging over a number of samples to get a "stable" output. In many cases, this averaging does not take place at all (missing), or takes place only in the C++ drivers that are present (need to be in the C version).

This needs to be implemented for all drivers that require it (check the existing UPM C++ drivers), and it should be implemented in the C driver. The "new" C++ drivers can just wrap the C implementation.