Add assert VI for disk file / folder verifications

[Nicolas Bats]

I make use of Caraya for source code unit testing but also for project folder disk testing and build results testing before packaging. I have created cutom additionnal defined assert VI to check disk hierarchy, for example (screenshot enclosed):

- Assert File Exists
- Assert File does not Exist
- Assert Folder Exists
- Assert Folder does not Exists
- Assert Folder is Empty
- Assert Folder is not Empty

but it would be great to have these VI "natively" in Caraya. It would be nice to have these new assertions in the `Assert.vi` polymorphic too.

Do you think it could be interesting?