Added mongodb authorization manager

I missed a proper authorization manager for mongodb. Since mongodb is perfect for storing tree-based structures, i made a very simple implementation for it. It overrides `CPhpAuthManager` and reads/writes into mongodb instead of a file. This was done before in other mongodb extensions, but I did it from scratch to be safe.

Currently it only supports multiple authorization configurations through collection names, but I don't think this is really needed.

Happy St. Nicholas Day!