Add titles to dashboard pages

[melange396]

Titles already exist for all of our pages and can be seen in the title for the browser window, but this is non-obvious. Create title headings at the top of dashboard pages, i.e. insert a line right below the navigation menu and right above the page content (for example, in the case of the "Delphi Epidata Dashboard" right above "Explore a LOCATION (or INDICATOR)". This should be applied to the Delphi Epidata Dashboard, and to "COVIDcast Dashboard (Classic)", as well as to other static pages or webapps that lack them.

(This was originally mentioned in #1000 (comment) )