Add Periodical, PublicationIssue, PublicationVolume

Add the types and properties 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>
Add Periodical types and changes to docs/full.html

Signed-off-by: Dan Scott <dan@coffeecode.net>
Add periodical and article examples

Having examples with descriptions that provide a rationale for the
existence of the example seems likely to be helpful to users of the
schema.org docs.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Give *Number series properties a consistent range

Per http://lists.w3.org/Archives/Public/public-vocabs/2014Aug/0140.html,
make issueNumber and volumeNumber accept a range of Integer as well as
Text, while relaxing episodeNumber and seasonNumber such that they will
accept Text as well as Integer.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Make *Number subproperties of "position"

Per http://lists.w3.org/Archives/Public/public-vocabs/2014Aug/0140.html,
make episodeNumber, seasonNumber, issueNumber, and volumeNumber
subproperties of position, and make CreativeWork the domain for
position. Adjust the definition of position accordingly.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Add periodical equivalence assertions for bibo

A number of the periodical properties and classes have clear equivalence
to Bibliographic Ontology Specification (bibo) counterparts.

While many of the classes and properties emerged organically, in the
case of pageEnd, pageStart, and pagination the properties were derived
directly from bibo; acknowledge that accordingly.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Merge branch 'master' of github.com:dbs/schemaorg into periodical_position
Enable tests to pass by adding a Unit.storePrefix() method

Currently the method does nothing, but parsers.py expects to be able to
call it when it encounters a prefix attribute when parsing
data/schema.rdfa, so let it at least not fail.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Use fully expanded URIs for equivalentProperty

Rather than messing around with prefix attributes and the parser,
fully expanded URIs just work. So let's go with that.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Merge pull request #17 from dbs/periodical

VOCAB: Add Periodical, PublicationIssue, PublicationVolume