Add local frame conversion for calibrated imu data (acc, gyr, mag)
Fix NameError: name 'ch' is not defined

if we get to that part of the code (discovered when compiling file with
the warning: undeclared name not builtin: ch)
Fix many errors of stuff not declared

In cases that never execute, it seems, but that can't be compiled from
cython if not fixed.
Remove xSens GPS references

We don't use this at PAL, and we don't have the gps_common package