Settings entry for highlight option (based on pull request #85)

This code adds an entry to the Papercite Settings page so that a user can set author/editor names to highlight globally.

*This request depends on successfully merging code from pull request #85* (https://github.com/bpiwowar/papercite/pull/85). I should probably have done this on a fork of @mhenze's fork... but thought best to avoid forkception.