move the lever mount spacer out of the panels, into separate part

this has two effects:

1. thinner and thicker spacers could be printed to accommodate
   preferences without having to reprint panels
2. I'm still testing this a bit, but by not having the spacer and panel
   be the same (partially hollow) part, I think the lever clickiness is
   a bit more pleasing to the ear

the second point is entirely arbitrary, so the first point is the real
benefit, despite me trying this because of the second

Signed-off-by: Brian S. Stephan <bss@incorporeal.org>

src/top-panel-inset-lever.scad

@@ -10,12 +10,10 @@ include <components.scad>
 module lever_panel() {
 	difference() {
 		// base plate
-		union() {
-			translate([0,-20,0]) panel();
-			translate([0, 0, -((panel_z/2)+(lever_mount_z/2))]) levermountbase();
-		}
+		translate([0,-20,0]) panel();
 		// holes to mount the lever
 		levermountholes();
+		levermountcountersinks();
 	}
 }