Should cr:FileObject subclass sc:DataDownload?

[csbrown]

The sc:Dataset spec suggests that the distribution property should be of class sc:DataDownload (which extends sc:Thing > sc:CreativeWork > sc:MediaObject > sc:DataDownload). cr:FileObject is defined as extending sc:CreativeWork. We are using cr:FileObject in the distribution property -- I think probably therefore it needs to extend sc:DataDownload. Probably this wont break any parsers, but would be 1) technically correct which is the best kind of correct and 2) provide a number of useful properties, e.g. the sha256 property which exists on sc:MediaObject but not on sc:CreativeWork.