DriveBase doc suggestions

[dlech]

Describe the issue
What is wrong or unclear?

Suggested improvement
How can we fix it or make it clearer?

• DriveBase class initializer: mention that wheel diameter is often printed on the side of the LEGO tire (if it says A mm x B mm, which is diameter?) and pin holes in beams are approx 8mm center-to-center in case you don't have a ruler handy, you can use that to estimate.
• The intializer API doc should also link to the "Measuring and validating the robot dimensions" section, otherwise it is easy to miss.
• Methods that don't have a speed parameter should mention the settings() method as the way to set the speed.
• The settings() method should mention the default values.
• Methods should document possible exceptions. For example, you get a ValueError if the angle in turn() is too large, but what is the largest allowable angle?

[laurensvalk]

• Explain that you can change the default turning direction by reversing the left and right motor arguments.
• Consider allowing sub-millimeter (floating point) dimensions. The low-level code implicitly supports this already anyway.
• Add code examples.

[laurensvalk]

Fixed and/or deferred to separate issues as needed.