Bugfix:
signed integer parsing for the following parameters that were incorrectly parsed as unsigned:
1-byte temperatures:
device.temperature (IO 6)
pcb.temperature (IO 32)
1-byte accelerometer:
x.acceleration, y.acceleration, z.acceleration (IO 49-51)
average.x.acceleration, average.y.acceleration, average.z.acceleration (IO 755-757)
2-byte values:
segment.ain.voltage.1, segment.ain.voltage.2 (IO 26, 33)
ot.sensor.temperature.1 through ot.sensor.temperature.6 (IO 144-149)
extnav.position.altitude (IO 419)
4-byte value:
can.maintenance.before.engine.hours (IO 520)
Negative values were incorrectly stored as big integer values.
