Warnings for repeated attributes

[billvaglienti]

In Protogen XML an attribute should never be repeated, but we don't check for that case; even though we do check if attributes are not recognized. Need to add the warning for repeated attributes.

[billvaglienti]

IT turns out that repeated attributes are a violation of XML, so what's actually happening is that Qt's XML parser is not properly enforcing XML rules. I'm going to punt on this one, its not worth it to write my own xml parser.