Support nested keys in update sproc $set

[graham-sportsmgmt]

It would be great to add support for deep properties in the update $set sproc. This would enable us to send in more complex updates such as {$set: {"inventory.location.primary.city": "Miami", "product.sku.upc": "0124236542321"}}

With the current version we can only modify root nodes of the document.

This would also be needed for mongodb parity (see docs)