Changed to follow recent agreements with the Ensembl RDF model to define each feature as a sub-class of SO classes, use sio:is-transcribed-from instead of sio:is-transcribed-into, use ro:in-taxon etc.
Also, features are typed by classes defined in the INSDC ontology, introduced a virtual sequence URI (#sequence fragment) to be separated from entry URI, changed to use insdc:topology and obo:so_has_quality for describing linear/circular sequences, use obo:so_has_part for exon URIs and sio:has-ordered-part for individual part URIs (which sio:refers-to exon URIs).