Extension hooks and skeleton of phongo, and basic bson implementation

optimization thing.
If the return value of a function isn't used then you can skip expensive processing/formatting of results of things.

Say we have a
```
MongoDB->findOne(array("ping" => 1)); // Force a roundtrip to server
```
We can skip the bson decoding of that return document as obviously its a wasted cpu time.

This isn't very used feature of PHP though :]