Add MongoDB Support

[tracend]

As known a MongoDB will return results with "_id" instead of "id"

Would be nice to create a Model and Collection that would extend the default with a custom parse method that would "normalize" the results with proper ids...

[tracend]

It is assumed that the reverse operation (restoring the _id attribute) can either be done with a custom sync method or on the server side before the query.

This is left for the application developer to decide. (currently not implementing)

[tracend]

This solution needs to be revised as separate Model/Collection generators is not viable, especially in contradiction to other extensions/plugins.

The _id that seems to be the core of the problem here should be "sniffed" during parse() and a flag in options should be set declaring the data as mongo, for subsequent requests - save() etc.