New joystick file for RC trainer

A joystick file to use an RC transmitter as a joystick for (for instance) the ARDrone.

Also, stabilization float_euler did not complie without the include...
Because in this file Int32Eulers and Int32Vect2 are used which are declared in algebra_int.h
When you compile for float_euler it says these types are undeclared, and adding the include solves it