DB Modifcations for study creation

- Made two columns nullable in study table (number samples collected/promised)
- Added affiliation column to study_person to reduce likelihood of name
  collisions
Add unique constraint to study_person
Add affiliation property to StudyPerson class

also changes lookups to be based on name/affiliation since that is the unique
constraint
Add affiliation to test db population script
Fix tests, add tests for affiliation

Modify study and command tests to expect new affiliation argument
Merge pull request #263 from adamrp/mod_db

DB Modifcations for study creation