Fixed QueryWrapper.ShouldContain assertion when QueryWrapper.Any() is false
More useful error message for QueryWrapper extension methods
Test broken by QueryWrapper.ShouldContain issue

Due to the incorrect id value written to the stream, the QueryWrapper
could not find the element required, but ShouldContain was passing the
test anyway.
Missing test for QueryWrapper.ShouldBeOfClass
Modified validator not found exception message to be more generic.