Issue 310: Multiple reference forms in a SecurityTokenReference

There are two parts to the proposal. 

1. This specification allows for the use of multiple reference
mechanisms within a single SecurityTokenReference. When multiple
references are present in a given SecurityTokenReference, they MUST
resolve to a single token in common. Specific token profiles SHOULD
define the reference mechanisms to be used. 

2. A thumbprint reference MUST occur in combination with a required to
be supported (by the applicable profile) reference form unless 
. a thumbprint reference is among the reference forms required to be
supported by the applicable profle, or
. the parties to the communication have agreed to accept only thumbprint
refererences.

Let us discuss applicabilty of the two parts to the specific issue at
our conf call tomorrow.
Thanks
Vijay