Session Token Working Draft 4

I have uploaded WD04 of the session token profile. I have responded to all the comments made by Scott, in most cases making the changes he suggested. Major changes include:

Processing algorithm is now normative (although much of it is still optional)
Subject is no more constrained that the SSO profiles, except confirmation is always bearer
Session start time is removed
Optional compression is allowed
Metadata and corresponding schema is defined

Hal