Hint for i2c Lcd 1602 example

Dear @kilograham,

I looked into the example of lcd1602 and one point came up.

This would be the perfect example making a lib kind of lcd class for the lcd and put only the relevant part in the main file.
Putting all stuff in the main file makes the example unclear from my point of view.

Also would beva good example here how to create a lib kind of an class an use it like in cpp.
