add: clarification about the levels where conformsTo is used.
add: clarify that void:inDataset is for RDF distributions
add: void:inDataset points to an IRI of type void:Dataset
add: clarify where dataset types are valid
Merge pull request #71 from nicholsn/master

Clarifications by @nicholsn. Not sure I agree with 0d9d66d74a613e95658b643507eb8c656486c57e though.