New library for AdafruitMotorShield v1 - please comment

I've rewritten the example code for the Motor shield containing the L293D+74HC595 chips. I hope this library may be useful, since it resulted in much smaller code and data sizes.

It's work in progress. I tested the DC (H-Bridge) motor parts to the extent used in the examples. The part for controlling 8 motors aren't tested yet.

Since this is my first library, I'd like some feedback on what I could/should change.

(Sorry for posting in the wrong section previously, even though nobody complained)