Recording and replaying

(This is based on #4, so this is only a work-in-progress until I've finished with that one.)

I've added the possibility to

- record what the camera sees to an `.oni` file
- run kfusion from an `.oni` file instead from a real camera.

This way, we can record the raw data while doing a recontruction, and replay the same reconstruction later, e.g. when we are no longer on-site and for tuning the algorithm. I plan to use it for publishing the scans I've made for benchmarking versus other KinectFusion implementations, e.g. KinFu from PCL.