LCD: Add capability to override LCD output pin assignments if pins moved

Hi Rhys,

Thanks for all your work creating and sharing these libraries, we really appreciate it!

We had a customer ask about using the LCD library with alternative pin assignments, so this commit adds an additional constructor overload to change the assigned display pins.

If you don't mind as well, I'd like to link this library from the LCD & Keypad shield homepage.

Regards,

Angus