[widgets] P+C spec doesn't normatively state whether attributes are required or not

[Arthur Barstow]

Since the schema and Authoring guidelines are both non-normative, the  
P+C spec is not clear if  an element's attributes are required or not.

The spec should clearly state, with normative text, if an element's  
attribute(s) are required or not.

-Regards, Art Barstow