Account for different scaling factor from different devives

It is reported that the different version of the AHRS/LSM303 compass are sending the data with a potentially different scaling factor. It implies that we can't directly compare all the data from all the DOMs.

km3compass should offer a way to manage that, and provide all the results in the most natural unit we can think off (Gauss?). Naively, I would consider that applying this correction in the calibration module would make sense.

Todo list :

• Identify compass variant -> using compass UPI, either LSM303 (no scaling,done in FW) or AHRS (factor 2.04)
• Provide scaling to Gauss in the calibration module