CLC-3989 Shorten migration filenames from 16 to 14 digits

https://jira.ets.berkeley.edu/jira/browse/CLC-3989

When updating to this code, all developers will need to run this prior to starting up on the new code: 
```
rake migrations:fix
```
And the same for production machines. This change obviously can't be done inside a db migration because it alters the schema_migrations table. I tried the db:migrate approach and it got really weird really fast.