Improve annotation file output

[MatthewWhiting]

The use of circles to indicate the size of the detections is a bit limiting. It may be better to draw a box around the spatial extent of the detection (in the way it is done for the ASKAP source finder).

Note that there will need to be a conversion done from pixel extent (xmin, xmax, ...) to WCS for the annotation file.

[MatthewWhiting]

Done. I've tried to go one better than the box suggested above. The format is now a series of lines outlining the borders of the detection (in a similar way to the moment map plots). The way this is rendered in kvis is not entirely satisfying (the lines are not lined up with the pixel borders), but it is good enough to give an idea of the shape of the objects.

Closing ticket.