mvc framework required to implement sponsor_osra_id

part of PT story https://www.pivotaltracker.com/story/show/75999516

- *** This does not create a sponsor_osra_id yet ***
- model with validation that 1 and only one branch or oganisation is selected
- migration to add organization reference to sponsor
- belongs to organization reference in model
- specs to check 1 branch or orgnaization has been selected
- fixed sponsor factory so it is valid against new criteria
- fixed feature files to  reference a branch so they can be valid
- changed active admin form to show the organization and branch drop downs
added generation of sponsor_osra_id functionality

part of PT story https://www.pivotaltracker.com/story/show/75999516
- added sequential_id field and osra_num field to sponsor table
- implemented tests for osra_num functionality
- implemented osra_num functionality
refactored validation to reduce amount of code

Part of PT story https://www.pivotaltracker.com/story/show/75999516
added spaces in between braces to comply with project coding standards

part of PT story https://www.pivotaltracker.com/story/show/75999516
improved wording on description of affiliation tests based on code review

part of PT story https://www.pivotaltracker.com/story/show/75999516
refactor improved clarity and intent of afilliation tests

part of PT story https://www.pivotaltracker.com/story/show/75999516
refactor of osra_num tests

part of PT story https://www.pivotaltracker.com/story/show/75999516
refactor osra_num test to improve clarity

part of pt story https://www.pivotaltracker.com/story/show/75999516
thanks @NikitaAvvakumov
used build_stubbed instead of build for branches and organizations

part of PT story https://www.pivotaltracker.com/story/show/75999516
refactored rspec to match our project coding style

part of PT story https://www.pivotaltracker.com/story/show/75999516
contstraint to ensure model valid between validity check and before_create

part of PT story https://www.pivotaltracker.com/story/show/75999516
Merge pull request #43 from PurityControl/sponsor_osra_id

mvc framework required to implement sponsor_osra_id