OPF metadata validation update for EPUB 3.0.1

Adds validation of rules introduced by EPUB 3.0.1

   * the restriction to only one `dc:type` element has been removed
   * the restriction to only one `dc:source` element has been removed
   * the `source-of` property was added with the single value "pagination" for identifying the source of page numbers. This property extends `dc:source`.
   * allow "record" as value of `link` `rel` attribute - but requires `media-type` set
   * allow `belongs-to-collection` and `collection-type` properties
        * meta with `b-to-c` either has no `@refines` or `@refines` another instance of `b-to-c`
        * `c-type` extends instances of `b-to-c`
    * allow `media:playback-active-class`
    * rendering-related rules (for metadata in the "rendition" vocabulary)

This PR also vastly improves the way vocabularies and properties are handled, via a new API (`com.adobe.epubcheck.vocab` package) based on `enum`s, type-safe and immutable collections.
Parsing of prefix declarations  and property values are now using this new API.