* removing visual-based heading styles from 'sr-only' DOM elements
* revising default certificate view h1/heading copy
* revising DOM elements to use main/aside semantics
* revised edX/platform logo link alt text
* removed extra share/take home header text
* synced up add to LinkedIn profile copy
Add the ability to generate "example" certificates to
test that certificate generation is working correctly for a course.
Add the ability to enable/disable self-generated certificates
on a per-course basis.
