Shake up the about pages a bit

 - move details and contact to their own pages
 - add contact to footer
 - change "gift" nomenclature to "payment"
 - add "example" and "where next" sections to /about
Good catch. I moved `charts.html.spt` to `charts.spt`, so it will answer to requests for both `charts` and `charts.html`. I agree we should standardize our approach. I think we should use `foo.spt` for all HTML resources. Eh?