Bug 1082798: Split out header and footer tests

We still load the homepage to run these tests, but we organize them into
more specific categories. This will help us find and update tests,
enable/disable related tests, determine which parts of the interface are
most problematic, and more.
Merge pull request #2907 from openjck/bug-1082798-organize-tests

Bug 1082798: Split out header and footer tests