Update copy of QTRSensors

[BlueAndi]

The current copy of QTRSensors contains e.g. no doxygen comments. Therefore important informations for the Zumo32U4LineSensors() are missing in the generated documentation, see e.g. public functions here https://pololu.github.io/zumo-32u4-arduino-library/class_zumo32_u4_line_sensors.html

The documentation is really worthful, especially for interesting guys with less experience.

Additional we get further feature improvements.

[BlueAndi]

@DavidEGrayson What do you think, is there a chance?