Color adjustment

[mzur]

Implement color adjustment similar to the feature of the image annotation tool. This can be implemented client-side with glfx.js just like in the annotation tool. If active, the annotation patches are replaced by canvas elements which are each processed with the configured color adjustment. Add the configurable values to a new sidebar tab that looks just like the tab of the annotation tool.

Thanks to @rvankevelaer for the idea!