Provide single-file machinestate.py on Github page

[TomTheBear]

• Use Github pages to provide the single-file machinestate.py generated at release (new tag of form vX.Y.Z)
• Generate main webpage with a list of all release versions (starting now, no older versions) and a 'latest' link
  • Add individual page per release, so that e.g. https://machinestate.github.io/v0.6.0 is possible.
  • Add a symlink so that the latest release points to https://machinestate.github.io/latest
• Remove machinestate.py from repository
• Add machinestate.py to .gitignore
• Update README for getting machinestate.py
  • Link to main webpage
  • Link to latest version
  • curl/wget command with the link to the latest version
• Add a way to specify a header and footer for the webpage so we can add some texts, links and the logo around the list of versions.