It is useful mainly in Pcbnew, to import a logo from Bitmap2component, without the constraint to create a file and use the fp editor. Also a bit of cleanup code. Fixes: lp:1820829 https://bugs.launchpad.net/kicad/+bug/1820829
Apply patch from Cirilo Bernardo with some minor changes: mainly allows also the solder mask layer and keep ref and value fields on the silk layer.