Tests should be aware of the Current Culture Info

Hello,

As i'm French, my CultureInfo.CurrentCulture is set to "fr-FR" while running tests.
But for some tests, especially for the ToString() methods, tests are write to check "en-US" Culture.
Although it will probably be a bit longer here, could you format this to be similar to what you did in the Vector2/3/4 tests, i.e. calling string.Format on each of the individual matrix elements? I think it would be a little more readable (but probably longer).