Fix breadcrumbs, and reduce template code

This pull request does two things: 

1. Rename 'Search' in the breadcrumbs to 'Home'. This fixes https://github.com/18F/foia-hub/issues/243

2. Both profile.html and parent_profile.html had a lot of common template code. That's been reduced into one file, and used through includes. This means we only have to make changes in one place. 

These two changes are related only in that they touch the same files.