Support xs:int for WFS feature properties.

xs:integer is an unbounded integer whereas xs:int is a signed 32 bits integer.
see : http://stackoverflow.com/questions/15336872/xsd-what-is-the-difference-between-xsinteger-and-xsint
The interpretation of what an xs:integer is can vary depending on the implementation. For example
Microsoft's System.Xml.Schema.XmlSchemaDataType.ValueType maps xs:integer to System.decimal
and xs:int to System.Int32
see : http://bytes.com/topic/net/answers/172493-xmlschemadatatype-xs-integer-system-decimal

This code change will remove any ambiguity when the property is known to be an int32.