Show orphans sponsorship status

https://osraav.atlassian.net/browse/OSRA-177

- add fields for sponsorship status & current sponsor (if present) to orphan show view
- add disabled sponsorship status field to orphan edit view
- create 2 new sponsorship-related methods in the Orphan model
- make step definition for 'Unable to change field' more versatile at the cost of complexity & brittleness - worth it?

OSRA-177 #Code-Review
I am assuming this has been implemented to prevent Demeter violations ?
Given the method `current_sponsor` should return a String if a relationship is present can the method just return a string such as "Not Currently Sponsored" if a relationship is not present.
This would prevent the need to litter if statements through your view / controllers ?