Simple 4-camera movie viewer

This is only two commits further than the py_bind pull request,
https://github.com/OpenPTV/openptv/pull/15
So if you already pulled that one, only two commits will be added.

It adds a small program that uses the Python bindings, as a test case and example of what can be done - and useful in itself :)

The viewer shows a 4-camera movie side by side. The README.txt file in the viewer/ directory explains more. A screenshot is attached below.

![movie_viewer](https://f.cloud.github.com/assets/75150/583838/10433b34-c903-11e2-9775-2a2f9d4d4445.png)