Recording and replaying

[nh2]

(This is based on #4, so this is only a work-in-progress until I've finished with that one, and it also looks much bigger than it is.)

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.