At present raspberry-dataserver/BatteryLLI.py uses popen to run
upower as a shell command and parses the output. This should be
replaced by the upower python script (I would have done this, but I
can't compile upower on the Pi to test it)

raspberry-dataserver/CommsCommon.py is modified to add new parameters to
BatteryFormat (bat1_percent and bat2_percent, both ints). All other
parameters in BatteryFormat are unchanged.