Fix an incorrect description of the assertion.
Fix an erroneous assertion description.
Add a try catch statement to prevent the test suite from dying silently.
Move `load` test helper into util.js.
Remove an erroneous setAttributeNS call.

This erroneous call should have made the test named documentimportnode14 fail but a bug in the core.js code (in the handling of namespaces) made the test successful. (In brief: documentimportnode14 checks that an attribute node which is created for a default value is not copied in an import operation. However, the setAttributeNS would replace the attribute node created for a default value with an attribute node created because a value was explicitly set, thereby violating the precondition upon which the test is based.)
*AttributeNS now treat empty namespaces as no namespace.
Support proper attribute ordering semantics.

As specified by http://dom.spec.whatwg.org.