added ACCUM_DISTANC record type to mark distance in recorded file to be used during replay/seeking
add default DOUBLE data serializer
add  SensorDataInput.isSeekable() to enable checking either ACCUM_DISTANCE should be emmited or not
ACCUM_DISTANCE to be displayed in MetersDisplayManger is now calculated by GPSDataFilter unless replaying a SensorDataInput.isSeekable()
add RoboStroke.isSeekableDataInput()
bumped LOGFILE_VERSION to 3
misc: organize imports
#62: adjust total distance backward when rewinding a seekable replay stream