Update onthisday Swagger spec
Update onthisday Swagger spec

Fixed a typo, actually reworded the description of the types.
Reordered the list of types to have all and selected come first.
I assume those are the two options we want people to use the most.
Added 404 and 501 response codes.

wikimedia/mediawiki-services-restbase,gwicke/restbase,wikimedia/restbase,gwicke/restbase,eevans/restbase,milimetric/restbase,cscott/restbase,inverno/restbase,inverno/restbase,eevans/restbase,Pchelolo/restbase,wikimedia/restbase,d00rman/restbase,milimetric/restbase,d00rman/restbase,cscott/restbase,wikimedia/mediawiki-services-restbase,Pchelolo/restbase