dev: extracted replicateDdocs and fixed a bug

Extracted replicateDdocs into a standalone file, so that it can be run
on it's own (e.g. when setting up a registry without replication).

Added 'registry/error: forbidden' to the list of replicated documents,
otherwise private npm-www does not work (fixes isaacs/npmjs.org#98).
dev/go.js: start elasticsearch and npm2es

Added elasticsearch configuration to dev/ folder and modified dev/go.js
to start elastichsearch and npm2es (npm to es synchronization).

Modified README.md to mention elasticsearch as a prerequisite.
Fix search debug output