Some changes suggested by Axel Neumann.

- Rewording of intro to challenges slide (also reversed title).
- Indicate interesting features of OpenWrt.
- Mention root access to containers.
- LXC is used to manage containers.
- Change title of experiments slide.
- Indicate minimum layer available to experiments.
- Mention IEEE P2P'12 demos.
- Indicate that DLEP and API experiments don't require slices.
- Also, API experiments will soon be supported, but not yet.