Special changes for Common @model and @context are available for review

Hi Everyone,

I added text to elements header, header/name, header/value, var and bind 
to indicate an xforms-binding-exception if a model other than the 
containing one was indicated.

I added text to rebuild, recalculate, revalidate, refresh and reset to 
indicate that they operate on the model associated with the in-scope 
evaluation context node.  Then, I added a note saying that one could 
change the model of the operation by using the model attribute, which 
changes the in-scope evaluation context node.

Lastly, I removed the text indicating that the model attribute was 
forbidden from all descendants of a model element, because the 
restrictions were made above and because it is probably not technically 
true since it could be used on actions within a model without causing any 
problems.

I also put the model attribute before context, because the model attribute 
affects the evaluation of the context attribute.

Next, I changed the context attribute to say that its first *node* 
replaces the context **item**, and **changes the context size and position 
to 1**.
So, I didn't change the word *node*, but I did change **item** (which used 
to also be node), and I added the bit about context size and position 
changing to 1.
I also said that the absence of the context attribute meant that the whole 
inscope eval context (not just the node/item) was not overridden.

Last, I added step 4 to the Evaluation Context method (
http://www.w3.org/MarkUp/Forms/wiki/XForms_2.0#Maintaining_Position:_the_Focus
), as this reflects the fact that @context is now a Common attribute.

Cheers,
John M. Boyer, Ph.D.
Distinguished Engineer, IBM Forms and Smarter Web Applications
IBM Canada Software Lab, Victoria
E-Mail: boyerj@ca.ibm.com 

Twitter: http://twitter.com/johnboyerphd
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