Add untouched SoftwareSerial from https://github.com/arduino/Arduino/pull/2032
SoftwareSerial: add ability to use only rx
Maxbotic: add library from https://github.com/Diaoul/arduino-Maxbotix
Maxbotix: make use of the improved SoftwareSerial version.

This avoids ISR conflicts between RxSoftwareSerial and SoftwareSerial.