Arch: Misc improvements to curtain wall

- Can be based on an edge like normal wall
- Now has a 'host' property to embed into another object (tree only)
- Mullions have different height and width properties
- Mullions or panels can be disabled

src/Mod/Arch/ArchMaterial.py

@@ -871,7 +871,7 @@ class _ArchMultiMaterialTaskPanel:
                 thick = FreeCAD.Units.Quantity(d).Value
             else:
                 thick = FreeCAD.Units.Quantity(d,FreeCAD.Units.Length).Value
-            th += thick
+            th += abs(thick)
             if not thick:
                 suffix = " ("+translate("Arch","depends on the object")+")"
         val = FreeCAD.Units.Quantity(th,FreeCAD.Units.Length).UserString