Add some DOMImplementation#createDocument tests from the DOM level 2 test suite.

The test now covers all assertions from

level2/core/createDocument01.xml
level2/core/createDocument02.xml
level2/core/createDocument03.xml
level2/core/createDocument04.xml
level2/core/createDocument05.xml
level2/core/createDocument06.xml
level2/core/createDocument07.xml
level2/core/createDocument08.xml
level2/core/domimplementationcreatedocument03.xml
level2/core/domimplementationcreatedocument04.xml
level2/core/domimplementationcreatedocument05.xml
level2/core/domimplementationcreatedocument07.xml