Simpleipv6

[timcoote]

This branch has two tags:

• ipv6lw is, essentially, documentation on how to use ipv6, with some example code.
• ipv6hw moves the code into robotremoteserver.py. This makes the default behaviour ipv6. Although this behaviour includes ipv4 as a subset, some of the notation changes, making this a breaking change. It would also fail on a platform that had no ipv6. I think that those are now quite rare.

I don't know what extra tests are required for these changes, but I think that the code in example is close to sufficient.

I don't know whether it's a hindrance, but this branch also includes the documentation changes on the semantics of the ipv4 address 0.0.0.0.