#2817 HAPI 3.0 servers should use dataset instead of id, try both, and migrate old URIs

[Jeremy Faden]

Eelco is writing a version 3 server, and it has a bug that it doesn't support the "id". I changed the code so that for version 3 both id and dataset are attempted. HAPI URIs can now contain the dataset= parameter, and old URIs will be migrated. (i.e. for HAPI URIs dataset= and id= are synonyms. Also version 3 servers will use dataset initially.