Initial work on the circle spectrograph.

Signed-off-by: Edward Minnett <eminnett@gmail.com>
The circle spectrograph is now rendering to image.

Added parameters to render as a taurus and render to a rotating image. This fixes frame rate issues and problems with clearing the canvas.

Signed-off-by: Edward Minnett <eminnett@gmail.com>
fiddling with tracks and colours

Signed-off-by: Edward Minnett <eminnett@gmail.com>