Implement LineGroups for default weights

- Add ability to control default weight for visible,
  hidden and decorative lines from a configuration
  file. Diffent sets of defaults can be specified as
  a preference.

src/Mod/TechDraw/App/DrawViewPart.h

@@ -98,6 +98,7 @@ public:
     App::PropertyFloat  LineWidth;
     App::PropertyFloat  HiddenWidth;
     App::PropertyFloat  IsoWidth;
+    App::PropertyFloat  ExtraWidth;
     App::PropertyBool   ArcCenterMarks;
     App::PropertyFloat  CenterScale;
     App::PropertyBool   HorizCenterLine;