U4-1083 Document type alias can be created the same.

I have fixed this by amending the validation function.
I also spotted the same bug when copying a document type. I fixed this one by adding the validation controls to it's page and adding it's corresponding validation methods. I also wrapped a Page.IsValid to the function that copies the document type.
I also spotted that the copied document type's name is not change so I fixed this too.

PLEASE NOTE that most of the line changes shown are due to visual studio formatting the page. (tabs instead of spaces etc.)