Feature/add pb rake tasks

**Background**
In iMedidata we have a useful rake task that checks if all our PB numbers are unique. I thought it would be useful to migrate that task into kender and include it as part of the ```rake ci:run```. Added tests for the new rake task as well. I actually didn't write the original iMedidata rake task that credit goes to @chad-medi. I'm just integrating what he wrote into kender.

All new tests pass. Currently, running all existing scenarios.

@mjobin-mdsol @asmith-mdsol Please review & merge when satisfied