Draft: add modules of draftfunctions to the proper Doxygen group

This includes `array`, `cut`, `downgrade`, `draftiffy`, `extrude`,
`fuse`, `heal`, `join`, `mirror`, `move`, `offset`, `rotate`,
`scale`, `split` and `upgrade`.

These are added to the `draftfunction` Doxygen group
so that the functions contained in each module are listed
appropriately in the automatically generated documentation.

src/Mod/Draft/draftfunctions/offset.py

@@ -20,23 +20,21 @@
 # *   USA                                                                   *
 # *                                                                         *
 # ***************************************************************************
-"""This module provides the code for Draft offset function.
-"""
+"""Provides functions to create offsets of different shapes."""
 ## @package offset
-# \ingroup DRAFT
-# \brief This module provides the code for Draft offset function.
+# \ingroup draftfuctions
+# \brief Provides functions to create offsets of different shapes.
 
+## \addtogroup draftfuctions
+# @{
 import math
 
 import FreeCAD as App
-
 import DraftVecUtils
-
 import draftutils.gui_utils as gui_utils
 import draftutils.utils as utils
 
 from draftmake.make_copy import make_copy
-
 from draftmake.make_rectangle import makeRectangle
 from draftmake.make_wire import makeWire
 from draftmake.make_polygon import makePolygon
@@ -244,3 +242,5 @@ def offset(obj, delta, copy=False, bind=False, sym=False, occ=False):
     if delete:
         App.ActiveDocument.removeObject(delete)
     return newobj
+
+## @}