Writable, Readable and Duplex streaming on collections.

[matt-filion]

const users: Collection<User> = new Collection(User);
const newUsers: Collection<NewUser> = new Collection(NewUser);
const transformer: DuplexStream = ....;

//This should read from users, transform using the transformer and then write to newUsers.
users
   .pipe(transformer)
   .pipe(newUsers);

• .pipe() should produce a ReadStream that makes use of .find with no prefix.
• Collection itself should implement WritableStream so it can be used as a value into .pipe() as a write destination.
• ReferenceList should have a .pipe() method to produce a ReadStream which will produce documents starting with the prefix defined in .find() provided to get the ReferenceList.