Support a cleaner print template format

[StevenTammen]

Similar to this other issue:

• Refactor theme to elegantly fall back to more barebones functionality in the absence of JavaScript and CSS #1

The print template for the site needs to be cleaned up as necessary, to ensure that things print well.

One obvious thing is removing the bottom mobile bar from the print template. But we also want special content sections showing up appropriately, and so on.

If someone wants to print a content page, they should be able to just open the print dialog and do it instantly. Whatever needs to be done to support that should be done.