Implement forward (fd) and left / right (lt/rt)

[campey]

Simplest implementation would be to have the parameter specify the duration in number of frames or seconds.

This is different to the behaviour of the logo implementation in the standard library turtle module.

One ideal would be to have them match by using feedback to notice when

The other perspective is that it is nice to have more direct experience of robot through timing.

I think the resolution here would be to use overloading, so the default behaviour of forward(100) goes forward 100 units, but perhaps slowly. To go faster could be done using named parameters for speed and time. And ultimately direct actuator control.