[Standards] Data Forms schema

[Brett Zamir]

For XEP-0004, in addition to the correction in the schema we discussed 
earlier on loosening element ordering requirements within <field/>, the 
schema dealing with <field/> also ought to be updated to allow for Data 
Forms validation children:

<xs:any namespace='http://jabber.org/protocol/xdata-validate'/>
or

<xs:any namespace='##any'/>


....if you want to allow more than just Data Forms Validation children...

Brett