Fixes #1089 - it shouldn't be possible to remove yourself as package owner if you are the last (only) owner. That would create an ownerless package (we have a bunch of those right now though).
Fix a broken test. Re fix #1089 to work for removing pending owners when there is a single non-pending owner. Add a unit test of 'won't remove the last owner'.
Merge pull request #1159 from NuGet/tilovell-1089-noRemoveLastOwner

Make it impossible to remove last package owner with json api