issue 6924: concrete proposal

Change the exposition of Put as follows:

A Put request MUST be targeted at the resource whose representation is 
desired to be replaced, as described in 2 Terminology and Notation 
<http://www.w3.org/2002/ws/ra/edcopies/wst.html#Notations_and_Terminology> 
of this specification.

Implementations MAY use the fault code wst:InvalidRepresentation if the 
presented representation is invalid for the target resource. The 
replacement representation may be considered to be invalid if it does 
not conform to the schema(s) for the target resource or otherwise 
violates some cardinality or type constraint. If an implementation 
detects that the presented representation is invalid it MUST generate a 
wst:InvalidRepresentation fault.

The replacement representation may contain within it element or 
attribute values that are different than their corresponding values in 
the current representation. Such changes may affect elements or 
attributes that, for whatever reason, the implementation does wish to 
allow the client to change. An implementation MAY choose to ignore such 
elements or attributes, or it MAY generate a wst:UpdateDenied fault. See 
5 Faults <http://www.w3.org/2002/ws/ra/edcopies/wst.html#Faults>.

Other components of the outline above are not further constrained by 
this specification.

A successful Put operation updates the current representation associated 
with the targeted resource.

Add the following fault definition to Section 5:

5.2 wst:UpdateDenied

*[Code]*  s:Sender
*[**Subcode]*
 wst:UpdateDenied
*[**Reason]*
 One or more elements or attributes cannot be updated.
*[Detail]*
 An optional list of the QNames of the elements or attributes that are 
not allowed to be updated.