Setting button for catalog overlays

[lmichel]

It would be useful to add a setting button (gear wheel) for the catalog overlays which would allow users to choose color/shape/size of the source markers.

Expected benefits:

• Optimise the visibility upon the background, which can have any dominant color
• Optimise the contrast between different overlays
• Facilitate the evaluation of correlations between catalog sources with either image features or sources from other catalogs.
• Avoid overlay between sources closed to each other

[tboch]

I fully support this request, I planned to add something similar to that:

in the regular Aladin lite UI.

[lmichel]

This looks good to me.