Always use the POST form of _changes, since CouchDB supports it
Always use the POST form of _changes, since CouchDB supports it

This avoids the potential of ridiculously long URLs if the replication
has a huge set of filter parameters, e.g. channel names.
Fixes #964

amco/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios