Swap usage of serif & sans fonts

Sans for headers, labels and serif for content.

* Increase letter spacing and line height.
Restyle orange button color usage

* Use light orange for default button state, darker orange for
hover event.

* Revert back to blue-button & orange-button selectors.
Move site disclaimer to its own page

* layout.jade: Refactor footer to include link to site disclaimer page.
* app.js: Wrap site_company, email_address in new site_owner object.
SEO: Add topic title followed by company name
Move search site input field to footer
about.md: Fix encoding issue