Add support for exporting mongoDB contents into elasticsearch

Added essync tool to manually export data from mongoDB into
elasticsearch. This work was done with jrwren.
Updated with review comments
Merge pull request #124 from mhilton/exportv4-cs-mongodb-into-es

Exportv4 cs mongodb into es

Added support for uploading mongodoc.Entity objects into elasticsearch and provide a tool to migrate them from an existing mongoDB database.
Added elasticsearch configuration to charmstore.

The config.yaml file can now contain an optional
elasticsearch-addr parameter specifying an
elasticsearch endpoint to connect to for searching.
Merge pull request #127 from mhilton/es-config

Added elasticsearch configuration to charmstore.

The config.yaml file can now contain an optional
elasticsearch-addr parameter specifying an
elasticsearch endpoint to connect to for searching.
lppublish, cmd/charmload: ingest exact revisions from legacy charm store