Support Elastica 0.20.x client

Breaks BC because of namespace change
Added field mappings into class metadata
Enrichment of SearchManager, ElasticSearch client, and serializer support

Mostly updates to ElasticSearch integration with breaking changes for
other clients. Also added support for more complex annotations, Unit of
Work style persistence, and support for different entity serialization
methods for persistence. Updated for Elastica 0.20.x support.
Skip object serialization during removal
Refactoring client interface clean up concrete classes
Support for Entity hydration, Pagination

Search manager now supports querying through a magic wrapper class.
Hydration is provided by default when an entity manager is provided
through configuration or injection, or directly through a custom
Doctrine Query if provided. Hydration can be bypassed to return search
results directly. Currently only functional for ElasticSearch.
Change default serialization callback
Code annotation cleanup
Remove pagination adapter
Fix hydration with empty search results
Change depency to ObjectManager
CS fix
Remove ORM dependency

Hydration query is now required to be specified if hydration mode is
not set to bypass.
Update method visibility
Merge pull request #77 from MrHash/master

Enhancement of ElasticSearch support, SearchManager, and Serialization