Fix PyPI Issues

[HughBlayney]

Fix discovered PyPI issues, including

• Dependencies weren't installed, as I had put them in the wrong part of the toml file.
• Images weren't showing, as they were using local paths.

Also updated a few small things; removed duplicated dependency (and other) information from setup.py, changed toml to get version from github tags.

Also adds a github action to build PyPI package based on github tags. This will have to be tested once merged, and is based on this guide.