added unique constraints to all osra_num fields at the db level

- any unanticipated duplicates of osra_num by the software will make the db
  reject input and the app to fail ungracefully
show sponsor name
duplicated for almost-obsolete AA.partner#show
Merge pull request #197 from PurityControl/osra-num-db-constraints

added unique constraints to all osra_num fields at the db level
Merge pull request #199 from theB264/sponsor_show_correction

show sponsor name
define model#self-descriptions