This CR provides support for maintaining public, private, and hashed data
This includes
   - An interface for managing the three categories of data

   - A default implementation that allows the use of either
     leveldb or couchdb. The default implementation uses a
     single logical db and uses different namespaces for
     different categories of data. Alternate implementation
     based on furture need or exploration should be easy to support.
     These may include using different dbs for different categories
     such as using leveldb for hashed data and using separate dbs in
     a couch instance for public and private data

   - If the underlying db does not support storing random bytes as key
     (for example couch supports onlu valid utf-8 bytes as key), the
     key for the hashed data is encoded using base64

Change-Id: Ia8ede4f4c0ab392119e59bb7f46e9c20062a411a
Signed-off-by: manish <manish.sethi@gmail.com>