new parameters for `rpcauth`
- `user_model` — specifies model that will be used to look up users through
- `user_filter` — dict of `.filter()` parameters to filter the queryset before looking up users
`noauth()` decorator, replacing authentication parameters with `None` without checking them
- allows both authenticated and non-authenticated RPC methods to have the same signature
`auth.AuthXMLRPCPoint` class for making authenticated requests
bugfix — exception info is always required, but was only collected when logging enabled
simplified `register_rpc` decorator
allow registering RPC functions with name different than the function name