remove autogenerated files

The received wisdom is usually that files generated at build time are
not checked into the repository. Remove the auto-generated message
headers and Python module.
.gitignore: add autogenerated message stuff

Add lines to ensure that the auto-generated message headers and Python
packages are not inadvertently added back to the repo.
Merge pull request #2 from rjw57/remove-autogenerated-files

Remove autogenerated files