Customizable overlap ratio (it defaults to 0.15 now)

lib/Slic3r/GUI/SkeinPanel.pm

@@ -57,7 +57,7 @@ sub new {
         },
         extrusion => {
             title => 'Extrusion',
-            options => [qw(extrusion_width_ratio bridge_flow_ratio)],
+            options => [qw(extrusion_width_ratio bridge_flow_ratio overlap_ratio)],
         },
     );
     $self->{panels} = \%panels;