Allow multiple images with same settings to be merged into a single job

[jvgogh]

Currently when creating a visicut project that imports multiple svgs that are then applied the same lasercutter settings (e.g. all engraved with same power & speed), each image is still emitted the lasercutter as a separate jobs, leading to additional manual steps needed when performing the cutting task.

it would be great to have an optional settings to merge all images that have the same config (mapping, position & laser settings) into a single job.