Log Message:
Update databases/couchdb to 2.0.0.

- The build system embeds the Erlang VM into the package, which means that
  the PLIST may differ across build systems. Hence why we use a semi-dynamic
  PLIST here.
- That also means that lang/erlang is now a build dependency only.
- Include a couch-epmd service for the Erlang Port Mapper Daemon using the
  embedded binary.
- Basic RCD script added.

Upstream changes since 1.6.x:

- Native clustering is now supported. Rather than use CouchDB replication
  between multiple, distinct CouchDB servers, configure a cluster of CouchDB
  nodes.
- Futon replaced by brand-new, completely re-engineered Fauxton interface.
  URL remains the same.
- The new Mango Query Server provides a simple JSON-based way to perform
  CouchDB queries without JavaScript or MapReduce.
- Mango selectors can be used in _changes feeds instead of JavaScript
  MapReduce filters. Mango has been tested to be up to an order of magnitude
  (10x) faster than JavaScript in this application.
- Rewrite rules for URLs can be performed using JavaScript functions.
- Multiple queries can be made of a view with a single HTTP request.
- Views can be queried with sorting turned off ( sorted=false) for a
  performance boost.
- The global changes feed has been enhanced. It is now resumable and
  persistent.
- New endpoints added (documentation forthcoming):
  - /_membership shows all nodes in a cluster
  - /_bulk_get speeds up the replication protocol over low-latency connections
  - /_node/ api to access individual nodes' configuration and compaction
    features
  - /_cluster_setup api to set up a cluster from scratch.
  - /_up api to signal health of a node to a load-balancer
  - /db/_local_docs and /db/_design_docs (similar to /db/_all_docs)
- "Backend" interface on port 5986 used for specific cluster admin \ 
tasks. Of
  interest are the _nodes and _dbs databases visible only through this
  interface.
- Support added for Erlang/OTP 17.x, 18.x and 19
- New streamlined build system written for Unix-like systems and Microsoft
  Windows

Upgrade Notes

- The update sequences returned by the /db/_changes feed are no longer
  integers. They can be any JSON value. Applications should treat them as
  opaque values and return them to CouchDB as-is.
- Temporary views are no longer supported.
- It is possible to have multiple replicator databases. replicator/db config
  option has been removed. Instead _replicator and any database names ending
  with the /_replicator suffix will be recognized as replicator databases by
  the system.
- Note that the semantics of some API calls have changed due to the
  introduction of the clustering feature. Specifically, make note of the
  difference between receiving a 201 and a 202 when storing a document.
- all_or_nothing is no longer supported by the bulk_docs API

See full release notes:

  http://docs.couchdb.org/en/latest/whatsnew/2.0.html