Added padding to custom.css to prevent page contents from being
displayed under the search bar.
Added an index page to serve as a welcome screen, with corresponding controller and test.
Merge pull request #20 from emma-burrows/welcome-page

Welcome page
Updated title link in header to point to the root of the web
application, rather than the root of the webserver.
Changed <object> to <img> for SVG files and added cache-period attribute
to static resources.