Improve tests, fix HyperLink order, add method ValidateDocument()

[PrzemyslawKlys]

This PR solves:

• As part of one PR, we found that the order of elements matters and we didn't notice it during the PR assessment. This PR adds a check right after document saving if there are any unexpected child elements. This should temporary work as an easy way to detect problems. In the long run document.ValidationErrors should be 0, but so far we have some issues to solve first
• changes order of elements in Hyperlink for Color, adds missing Value
• Add method ValidateDocument() with ability to define file format. Default is Microsoft365.