ADDED arc, circle and rectangle shapes for schematic. Shapes support
line styles and fill colors.
CHANGED sheet background color in Edit Text & Graphics Properties to
fill color (and it now affects shapes).
Pushed STROKE_PARAMS down into common and moved all shapes to using it
for stroke descriptions.
In P-CAD they don't avoid other copper pours, so this should more
accurately reflect that in Kicad. (Note that only the very-high-
priority part is new; we've always coverted them to zones.)
Fixes https://gitlab.com/kicad/code/kicad/issues/3997