mypy: Organize config file a bit, since it's grown.

mypy.ini

@@ -1,18 +1,20 @@
 [mypy]
-check_untyped_defs = True
-disallow_any_generics = True
-
-follow_imports = silent
-
-strict_optional = True
-# This is a more explicit supporting form of strict-optional:
-no_implicit_optional = True
-
+# Logistics of what code to check and how to handle the data.
 scripts_are_modules = True
 show_traceback = True
 cache_dir = var/mypy-cache
 
+# Options to make the checking stricter.
+check_untyped_defs = True
+disallow_any_generics = True
 warn_no_return = True
+strict_optional = True
+no_implicit_optional = True
+
+# Options to make the checking *less* strict, which we
+# might ideally eliminate.
+follow_imports = silent
+
 
 # REQ returning None issue