Bundled images are the author's own; about.html still holds the author's biography #669

Problem

#660 replaced the personal text defaults, but a fresh install still ships and uses the original author's pictures:

• www/img/profile.png is the default landing page image.
• www/img/hero_rigolet.jpg is the hero of the seeded About page.
• www/img also contains jason.jpg and two other personal photos.

themes/default/templates/about.html still has the author's biography hardcoded. Nothing routes to it (Blog.About is not registered), so it is dead rather than visible.

Fix

• Replace the default landing image and About hero with neutral artwork (or none), and remove the unused personal photos from the image.
• Delete about.html and Blog.About, or make the template render the About page's own content.

Follow-up to #657 / #660.