Add extra validations for all models ...

- Includes specs using the Shoulda gem
- Includes a refactoring of update_numbers to a "sortable" abstraction

updated org links to use same logic as template links. display org name if no logo ...

removed unecessary line form orgs controller

fixed linter complaint

fixed tests broken by org.links addition

Merge pull request #922 from DigitalCurationCentre/issue869 ...

Issue 869