8201 - Clarify required and optional operations

http://www.w3.org/Bugs/Public/show_bug.cgi?id=8201

I had an action item from the previous meeting to write up a more concrete proposal for this issue. Here is a suggested text for WS-Eventing. The same pattern can be applied for other specifications.

[1] Proposal for WS-Eventing

Add to Section 3.5 Compliance:

Subscribe, Renew, and Unsubscribe  operations defined in this specification MUST be supported by compliant implementations. GetStatus and SubscriptionEnd operations defined in this specification are optional and MAY be supported by compliant implementations.