Reindent tests in DOMImplementation-createDocumentType.html.
Add some DOMImplementation#createDocumentType tests from the DOM level 2 test suite.

The test now covers all assertions from

level2/core/createDocumentType01.xml
level2/core/createDocumentType02.xml
level2/core/createDocumentType03.xml
level2/core/createDocumentType04.xml
level2/core/domimplementationcreatedocumenttype01.xml
level2/core/domimplementationcreatedocumenttype02.xml
level2/core/domimplementationcreatedocumenttype04.xml
Merge pull request #1307 from Ms2ger/createDocumentType

Add some DOMImplementation#createDocumentType tests from the DOM level 2 test suite; r=gsnedders