Improve Observation fixture set.
Improve Observation fixture set.

* Fix bug: add thumb to fixture with images but no thumb.
* Add Comments to help avoid creating new bugging fixtures.
* Add more fixture Defaults.
* Remove attributes which merely repeat schema defaults.

pellaea/mushroom-observer,JoeCohen/mushroom-observer,MushroomObserver/mushroom-observer,JoeCohen/mushroom-observer,pellaea/mushroom-observer,pellaea/mushroom-observer,JoeCohen/mushroom-observer,JoeCohen/mushroom-observer,JoeCohen/mushroom-observer,MushroomObserver/mushroom-observer,pellaea/mushroom-observer,raysuelzer/mushroom-observer,MushroomObserver/mushroom-observer,raysuelzer/mushroom-observer,JoeCohen/mushroom-observer,pellaea/mushroom-observer,pellaea/mushroom-observer,MushroomObserver/mushroom-observer,MushroomObserver/mushroom-observer,raysuelzer/mushroom-observer,JoeCohen/mushroom-observer,MushroomObserver/mushroom-observer,MushroomObserver/mushroom-observer,pellaea/mushroom-observer,raysuelzer/mushroom-observer,raysuelzer/mushroom-observer,raysuelzer/mushroom-observer,raysuelzer/mushroom-observer