Server namespaces

Traditionally the computation route on the server accepts and executes a Blaze computation on the stored data source. 

    request = {'expr': some-json-representation-of-blaze-expression}

We add the option to provide a namespace to the request.  Blaze will substitute values accordingly.  This is useful for parametrized expressions where the parameters are stored separately.

    request = {'expr': some-json-representation-of-blaze-expression,
               'namespace': {'parameter': value}}