Improve metadata to match package conventions

[camdez]

• Tidy up headers.

• Use meaningful keywords.

  "The name of this field is unfortunate, since people often assume it is the place to write arbitrary keywords that describe their package, rather than just the relevant Finder keywords." -- https://www.gnu.org/software/emacs/manual/html_node/elisp/Library-Headers.html

• Add Homepage.
• Fix "ends here" footer format.