Aiowamp

Changes:
- Provisional `wait_until_done` methods to wait until a session/client is stopped.
- Call timeouts
- Sharded subscriptions and registrations
- URI match_policy is now respected by all methods that have a `match_policy` parameter.
- Invocation error handling for exceptions during the starting phase
- Removed aiobservable dependency in favour of simple message callbacks.

Fixes:
- bwlist \_\_contains__ check
- multiple registrations / subscriptions with the same URI are now possible

Added templates

Changes:
- Passing `aiowamp.SubscriptionEventABC` instance to subscription handlers instead of event message.
- `aiowamp.InvocationABC` and `aiowamp.SubscriptionEventABC` now provide the "registered" URI and the actual URI that spawned them (this matters for pattern URIs)
- "msg.pyi" file included in distribution.
- Custom Exceptions for error URIs
- Converting exceptions raised in procedures to proper error messages
- Black- and Whitelisting for publications
- Authentication (CRA, ticket)

Fixes:
- Built-in messages convert strings to URIs where necessary

First usable version, here we go.