Add "NonWhiteSpaceString" (Or Other Suitable Name!)

[robcthegeek]

We end up seeing guard clauses for string.IsNotNullOrWhiteSpace all the time (with their accompanying ArgumentException).

This should be easy - let's add NotNullOrWhiteSpaceString (or something shorter if I can think of a decent name!)

Suggestions welcome 😉

[robcthegeek]

Good suggestion from @chrisabird - NotEmptyString. We use this all the time and I want to save my poor hands! 👐 😄