[TD]assorted Preference updates

- section line convention label
- remove superfluous save/restore on changeEvent
- change default scrub count
- add preference for default symbol dir
- add preference for display of section cut line

src/Mod/TechDraw/Gui/ViewProviderViewPart.h

@@ -53,6 +53,7 @@ public:
     App::PropertyBool   HorizCenterLine;
     App::PropertyBool   VertCenterLine;
     App::PropertyBool   ShowSectionLine;
+    App::PropertyBool   IncludeCutLine;
     App::PropertyEnumeration   SectionLineStyle;
     App::PropertyColor  SectionLineColor;
     App::PropertyBool   SectionLineMarks;