Merge branch 'project-header-titles' into 'master'

Project header titles

Fixes my issues with !1293, see [my comment](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1293#note_2112289):

> No please, not this huge if/else statement again! This will get out of sync so quickly, like happened with the original page titles before the page_title helper per page :(

cc @haynes 

See merge request !1328