Add prjxray + prjxray-db information to htmlgen.py output

Currently you don't know what version of the tools generated the output and it makes hard to track down small issues.

Start in htmlgen.py, the entry point named in the issue, and trace how the HTML output is assembled. Add identifying version information for prjxray and prjxray-db to the generated output, then verify that the output makes both tool versions visible.

Written by the indexing model from the issue text.