Some UI tweaks

Moved stuff out of the header, footer, shim partials. I don't think it adds much to have these in their own partials. Things may change as the navigation grows in complexity (and we add code to correctly highlight the active section, only show certain links based on the user's roles, etc.), but even then, I'd recommend having a navigation partial rather than a header partial.

Also moved main content and footer into div.container so that Bootstrap would center the page and give us some left and right padding. I see now (after making commits) that you had 150px padding on top for narrow browser widths (which I set to 70px, which now looks wonky on phone sizes). Bootstrap provides a way to make nav elements appear in a dropdown list for small browser viewports. We can add that tomorrow.