[#82700892] Admin can save DOI pattern & number for a journal

https://www.pivotaltracker.com/n/projects/880854/stories/82700892

- DOI saves to database. DOI shows after page refresh
- adds a migration which adds 3 columns
- binds DOI information to the journal model in ember
- tests the rails model for doi stuff
- allows many papers to have no DOI information; includes tests
- close #615