GUI Updated, Read and Write Calibration file

GUI has been updated to more easily see current and new calibration
values.  Can now calibrate both accelerometer and magnetometer and save
calibrations values calibration.h file used by FreeIMU library.  There
seems to be an OpenGL memory leak or bug that makes the program slow or
crash when sampling and calibrating data multiple times in a single
session. Because of this, the program disables the buttons to collect
data and calibrate after running once.  Therefore, you must run the
program twice, once for each sensor if you wish to calibrate both
sensors, although you don't have calibrate both sensors if you do not
wish.