Measurement Tool: Style for ROI

[donald]

The ROI tool would be enhanced if the ROIShapes could have the concept of styles associated with them. This could allow the user to select a style or have a style selected for ROIShapes depending on image stats, if the image is bright, automatically have a darker line style or lighter one if the image is dark.

It would also be helpful if we could associate styles with creation buttons, then different buttons, creating the same shape could have different colours, etc. This would be very useful for instance in creating the first version of the spot counting tool.