Implement 1.3.6. /db/_find

[Stwissel]

Part of #29 Details: https://docs.couchdb.org/en/stable/api/database/find.html#

find needs special treatment since it uses transfer encoding chunked

Propose to use the Reactive pattern and use an Observer

Call would return something like CouchdbFindResult with meta information and the documents call the observer's on next. When onComplete gets called the Promise of CouchdbFindResult complets

[Stwissel]

Need to verify that chunked is used