[builder] set simulation camera properties

Make sure the CameraFP has always the same resolution,
and not the one of the last camera added.

Resolution: 800x600, focal: 25mm.
[builder] Set a field _node_name in environment and use it accordingly

In particular, it fixes the code for multi-node scene with cameras.
[builder] allow external node as viewers
[camera] handle multi-node

This fix a crash when adding camera in multinode
[builder] disable Bullet on non logic scenes
[pymorse] fix bug of Python 3.2 [Ubuntu 12.04]
[doc] homepages is not persistent
[bin] Fix an now invalid use of prefix

Reported by mirkodaniele dot comparetti at polimi dot it.