add Filter method which returns exception based on the unmatched value

[OlegKleyman]

This PR is to resolve issue #69

It adds a new Filter method to the Option<T, TException> class. The method is public Option<T, TException> Filter(Func<T, bool> predicate, Func<T, TException> exceptionFactory) and its goal is to allow the propagation of the unmatched value to the exception factory Func thus allowing the value in the optional to be used to create the exception when filtering fails to match.

I appreciate your time in taking a look at this PR.

[Clindbergh]

I think a 2nd method public Option<T> Filter(Func<T, bool> predicate) that empties the Option without producing an exception would be a useful addition.