ENH: Added Python library for CouchDB connection

CouchDB is a NoSQL database that provides document-based data storage (http://couchdb.apache.org/). It complements Slicer's file-based and SQLite-based data storage solutions.

Couchdb-python is a small native Python client library that makes database access very convenient:
https://github.com/djc/couchdb-python

This commits adds this small Python package to the Slicer installation package, similarly to
python-async python-chardet python-gitdb python-GitPython python-nose python-pydicom python-PyGithub python-smmap.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25706 3bd1e089-480b-0410-8dfb-8563597acbee