Choose the property name for key of collection.

[cHullaert]

I think I code and pull a bit faster.

My idea of feature was to add the capabilities to choose the name of the property for the key of a collection instead. My context is that I've already have a domain with key with name uuid instead of id.

So I started to develop' something base on your code and I submit my request. (Pull request #159)
My development is inspired on the createDb method, I had a method to specify the name of the key.

[wardbell]

We need this too. I'll be looking at your PR #159 and hope to accept it. If I can't, I will provide an alternative to achieve the same effect. Thank you.