Sponsor affiliate validations

OSRA-209 https://osraav.atlassian.net/browse/OSRA-209
SponsorType must match affiliate type

- validate that sponsor_type matches affiliate on sponsor creation
- make sponsor_type, branch & organization readonly in sponsor
- disable selectors for Sponsor Type, Branch & Organization on the Sponsor Edit page

- update seeds, specs & features to conform to the new validation
This must be RubyMine's new formatting defaults. I suppose it indents the second line with respect to the start of the receiver for the method chain (here, `validate_...`). I'm seeing a lot of this in @motasem-salem's #108, and I think he uses RubyMine too. I'm not opposed to it enough to volunteer to clean it all up, but will respect the team's opinion :)