Lock taxon photos for the most-observed taxa

iNat changed the default - so that when we choose taxon pictures, the default is now RG. I have also replaced pictures which came from Flickr where the ID is doubtful, in favour of an iNat RG obs - where the ID will change if an identifier has good reason.

https://forum.inaturalist.org/t/suggestions-towards-more-accurate-taxon-default-photos/8066/9
2019 - sorry can’t find the RG announcement

https://forum.inaturalist.org/t/misidentified-photo-is-default-for-a-species-but-only-link-is-to-flickr/5712