VOCAB: Add Periodical, PublicationIssue, PublicationVolume

Add the types, properties, and examples per
http://www.w3.org/wiki/WebSchemas/Periodicals,_Articles_and_Multi-volume_Work
along with the modifications for existing types and properties, per discussion
on public-vocabs.

Signed-off-by: Dan Scott <dan@coffeecode.net>