Initialize implement notin join

Static Helper in place with a first join (Not In join) to test usage:

with simple scalar values:

      var wrapped = new ListElementsWrapper<int> (new []{ 1, 2, 3 });
      var joinList = wrapped.NotIn (new List<int>{ 1, 3 });
      Check.That (joinList).ContainsExactly (2);

or with objects of the same type:

 	var sut = ForElements
		.In (SampleData.Source)
		.NotIn (SampleData.Modified, x => x.Id);
	Check.That (sut.Properties ("Id")).ContainsExactly (2);