Refactored Perimeter code with new Slic3r::Polygon and Slic3r::ExPolygon objects

Large refactoring. Speed gains. Removed convex hull for bridges.

lib/Slic3r/Line.pm

@@ -65,4 +65,9 @@ sub parallel_to {
     return Slic3r::Geometry::lines_parallel($self, $line);
 }
 
+sub length {
+    my $self = shift;
+    return Slic3r::Geometry::line_length($self);
+}
+
 1;