Configurable Mountpoint

Added configurable mountPoint (/context/db) URL prefix handling to middleware used by app so that action is not taken when incorrect URL is used.  For instance, this handling will see to it that nothing is stored in GridFS unless the correct context (/ecrud/v1) and db (core or audit) is used).  The context set with config.context (defaults to '' if not specified), and the db is set with config.db.name.  The mountPoint then is config.context + '/' + config.db.name.