Prevent date properties from being incorrectly cloned when specified as a projection

[microadam]

With a document like:

.insert({ _id: 'a', date: new Date() })

and a find like:

.find({}, { fields: { date: 1 } })

Document is returned like:

{ date: {}, _id: 'a' }

This fixes the problem

[kofrasa]

Thanks for the patch Adam. It will be nice if we could generalize this for other constructor based objects though. This looks like something that we may have to repeat for other user-defined types that are not simple objects. Doing so will also allow the Backbone integration to continue to work properly which also currently breaks as you have just revealed.