Normalize xsi:type attributes

[nikku]

XSI type attributes contain namespaced information; normalize the attribute values accordingly.

<foo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://foo"
     xsi:type="bar" />

With the following namespace configuration:

parser.ns({
  'http://foo': 'FOO'
});

... the parser should normalize attrs to { 'xsi:type': 'FOO:bar', ... }.