OGM-262 Add integration with CouchDB

https://hibernate.atlassian.net/browse/OGM-262

Follow-up of the previous pull request: https://github.com/hibernate/hibernate-ogm/pull/194

I've rebased and applied a few minor changes (converted a RunrtimeException to a method in the logger  and renamed a couple of contants).

@dreab8 could you check that everything still looks good?
@emmanuelbernard could you take a look at it and let me know if It can be merged eventually?

Cheers