MultiMatch Fields needs Fields(Fields fields) overload

[Mpdreamz]

Double check wherever we expose a Func<FieldsDescriptor<T>, IPromise<IFields>> folks can also specify Fields directly in the fluent dsl

[Mpdreamz]

We consistently don't do this anywhere now but

x.Fields(f=>f.Fields())

Would be nice to also support

x.Fields(Field<Project>(f=>f.Name).And(f=>f.Description))

Everywhere