Updated void file from Zepheira

From @erimille , on issue #34:

This VOID file

simplifies the description to focus on the more common best practices for constructing VOIDs.
Removes provenance and updates details for the time begin (there are several ways this can be added and we can weave these in as needed moving forward)
License has been defined as CC0 per F2F discussion
Owner / Creator / Publisher defined as US NLM (useful for discovery)
Added "Linked Data" to description (as that is anticipated useful from a discovery perspective of aggregate VOID files)