NTFY-153 Added some new error messages for Storage

Added a couple new error messages
NTFY-153 Added a function to get a database connection via the current strategy

Storage requires a simple connection, upon which gridfs will do it's own
collection configuration. We would still like to use whatever the
current strategy is for caching connections, and this previously wasn't
exposed
NTFY-153 Documentation change

Converted to javadoc format