Take a panoramic photograph of a site

[mdepp]

We need a way to take a panoramic photograph of a site. At minimum it should be 180 degrees, but ideally it would be 360 degrees. There are at least two ways this could be done:

• we could use a bunch of cameras pointed in separate directions and stitch the images together
• we could use a single camera and rotate the rover in-place

Once we've decided on how this will be solved, we need to create a node to implement it (it's probably a good idea to separate out the image processing code from the other ros code, so it can be developed and tested first).

This is needed for the prospecting task.