RE: ISSUE-163, standalone XSD and RNG schema needed for Signature Properties

> I checked in a draft xsd schema file after extracting the schema from
> the examples and starting to try to fix some errors, in case that
> helps an easier start:
> 
>
http://www.w3.org/2008/xmlsec/Drafts/xmldsig-properties/xmldsig-properties-
> schema.xsd

A valid version is attached, with the following changes:

- fixing some errors and missing prefixes
- removing extra type definitions when the element is just a string or
dateTime

In addition, I would suggest changing the two properties that are empty
elements with the URI attributes into elements with a type of anyURI and
just putting the value into the element.

Note that I'm also just correcting the schema as given, and since there are
no examples in the document, I can't tell you for sure whether the XML you
*want* is represented.

-- Scott