Fix dc:type and dc:source rules for EPUB 3.0.1

The restriction to only one of these elements has been removed.
Added one test case for each element.
Simplify tests with a @Before setup  method
Add support for the 'source-of' OPF metadata

  * added it to the list of known properties
  * added Schematron checks for:
     * its allowed value
     * must have a `@refines`
     * the @refines target must be `dc:source`
  * added tests
Support for 'record' link elements (3.0.1)

  * link elements of type 'record' are now allowed
  * they must have a `media-type` attribute (schematron test)
  * they must not refine another property or element (schematron test)
Support collection-related OPF metadata

 * add 3.0.1 'belongs-to-collection' and 'collection-type' properties
 * 'belongs-to-collection' must either be publication-metadata or
   refine other 'belongs-to-collection' properties (schematron)
 * 'collection-type' must refine a 'belongs-to-collection' property
   (schematron)
Add support for vocabs
Improve prefix parsing

 * parsing is now done in `PrefixDeclarationParser`
 * parsing better supports edge cases and invalid characters
 * vocabs are computed in `VocabUtil#parsePrefixDeclaration`
 * added several new prefix-related error codes
 * thorough tests
Add known vocabs
Split property parsing into list & single-value
Integration of revamped vocab/property handling

  * Parsing of prefix declarations and property values are now done
    with the `com.adobe.epubcheck.vocab` utilities
  * Replace old constant maps with enums and immutable collections
  * Fix tests accordingly
Support for 'rendition' metadata checks

All check are implemented with Schematron.

Note: the requirement that viewport dimensions are declared for
pre-paginated content is currently not validated.
Merge pull request #430 from IDPF/feature/301-opf

OPF metadata validation update for EPUB 3.0.1