Individual motors test

Individual motor test: Gives the user the possibility to test arbitrary motor by submitting an argument to motors cmd.

By submitting an argument containing the motor number the corresponding motor will spin until user presses any key. For example "motors 1" will spin the motor connected to output 1. Motors command without any argument works the same way as before.
Changes in test.pde, AP_MotorsMatrix.h and AP_MotorsMatrix.cpp