Either and Either functions added
 - count, forall, fold, exists, map, bind, ToList, ToArray

Option, OptionUnsafe, Either, and EitherUnsafe are now IEnumerables.

Added LINQ tests combining IEnumerables with Option, OptionUnsafe, Either, EitherUnsafe and TryOption.
Merge branch 'master' of https://github.com/louthy/CSharpLanguageExt.git