couch_replicator: add replication using changes in a view

Instead of a database, the replicator can now filter the documents using
a view index. All documents having a key emitted in the view can be
replicated.

View parameters can be used. Which means that you can replicate results
corresponding to a key in a view or a range.

Conflicts:
	src/couch_replicator.erl
	src/couch_replicator_api_wrap.erl
don't replicate removed document in a view changes

Conflicts:
	src/couch_replicator.erl
	src/couch_replicator_api_wrap.erl
fix view changes with multiple keys

Conflicts:
	rebar.config
	src/couch_replicator.erl
remove old rcouch code