Documentation upgrade

[lfarv]

The just-released PyAT 0.2.2 shows a few errors in the project description (mainly outdated web links or AT commands). This updates the package build and documentation:

• Update the links to Web sites,
• Update pyat_examples.rst,
• Trigger the build of wheels only for numeric tags. This allows creating tags like "pyat-latest" without triggering a full build. Testing the build sequence is now available by triggering the "build-python-wheels" action from the GitHub interface.