Improve ScanPlot2d

This MR provide few fixes plus widget to use features from daiquiri!352 (merged)

• daiquiri!352 (merged) have to be merged first
• Added widget to select LUT/normalization/autoscale
• Display console.error when the image can't be loaded
• Code clean up

Here we can see that the image is properly displayed, which is not the case without this MR.