Durable subscription browser

Many if not all JMS providers give the ability to programmatically browse messages undelivered to a client on a durable subscription. Some do it via a custom API, some via JMX.

A standard way of doing this for all providers would make tooling easier.
#### Affected Versions
[1.1]

Start by reviewing the Jakarta Messaging 1.1 specification and the issue's examples of provider-specific APIs and JMX. Compare how providers expose undelivered messages for durable subscriptions, then define what a standard browsing capability would need to cover. Done means a decided, provider-independent design suitable for tooling.

Written by the indexing model from the issue text.