Adds titles to anchors for accessibility win

For accessibility reasons anchors should always have titles. 

This is just a start but this commit adds anchor titles to linked article titles and category / parent category titles in article views, category and featured blog views, and to logo and back-top link in Protostar.

I would have loved to add titles to readmores as well but, with the access restrictions on those elements, I'm unsure how to best do that.