More fixes for mdn due to redesign

One fix to the profile page, a lot of changes to link locators in the header, and attempts to fix all tests for the home page.

I removed some tests which are for menu items that are no longer present. We may want to add some tests for the lists of links in the content area of the home page.

Two of the visibility tests are currently failing, as they are both based on menus that pop up. I haven't had time to address them yet, but I wanted to finish this piece of work, get it committed and, hopefully, merged into master.

There is definitely lots more to do.