View layout & style tweaks

Added a helper to app.rb for creating nice page titles. Updated layout
and most views to use it.

Moved bootstrap container and footer to layout. Previously, pages
included both the div for the container and the footer. This allows the
footer to be updated without having to update individual views.

Major styling & layout tweaks to 'main_page' view. It should look
better.
Added '/api/login' route for non-browser clients

This route was previously removed because it had redundant auth code.
The auth code is now in a helper method and /login and /api/login call
it.

I'm currently testing admin automation using rest-client. User auth
currently uses cookies, and rest-client is unable to get the cookie w/
session info when POSTing to /login due to its redirect to /main.

/api/login does not redirect, so rest-client can get the cookie from its
response.

Browser clients will continue to use /login, as it's easier and
requires no JavaScript.