Draft: clean up code, PEP8, and docstrings in PathArray

Test the inputs to the `make_path_array` function
and return `None` if there is a problem.

Now the make function accepts as input a `"String"` which must be
the `Label` of an object in the document, so it is easier to create
arrays quickly from the Python console.

Add the new parameters to the make function, `align_mode`,
`tan_vector`, `force_vertical`, and `vertical_vector`.
These properties were added to the proxy object in ff323ebdb5.

Add  message deprecating the older call `makePathArray`.

Adjust the GuiCommand accordingly. Now it uses the commit
mechanism of the parent `Modifier` class so that the executed
functions are recorded in the Python console.

Clean up the `PathArray` class as well.

src/Mod/Draft/drafttests/test_modification.py

@@ -468,11 +468,13 @@ class DraftModification(unittest.TestCase):
 
         number = 4
         translation = Vector(0, 1, 0)
+        subelements = "Edge1"
         align = False
         _msg("  Path Array")
         _msg("  number={}, translation={}".format(number, translation))
-        _msg("  align={}".format(align))
-        obj = Draft.make_path_array(poly, wire, number, translation, align)
+        _msg("  subelements={}, align={}".format(subelements, align))
+        obj = Draft.make_path_array(poly, wire, number,
+                                    translation, subelements, align)
         self.assertTrue(obj, "'{}' failed".format(operation))
 
     def test_point_array(self):