LUCENE-3312 Break out StorableField from IndexableField

by Nikola Tanković for Apache Software Foundation

Lucene is a open-source full-text search library written in Java, but ported to many other languages. It relays on concept of document, a core Lucene information holder in need to be indexed or stored. This project will decouple indexing and storing operations over fields in document, as well as separate document classes in indexing and search time.