lang/org: major refactor

The motivation for this change was to rethink lang/org's flags. Many of
its former flags represented non-features. Therefore, its flags have
been reduced to five: +dragndrop, +ipython, +pandoc, +gnuplot and
+present. Everything else is included as org-load-hooks and treated as
reasonable defaults.

Other changes:
- Fixes #1502: don't autopair certain pairs when in a math region
- Fixes #1483: broken localleader in org-agenda
- Adds gnuplot support #1108
- Doom's org submodules have been moved into lang/org/contrib/, because
  I expect there will be *many* more to come, and I don't want to
  pollute the moudle's root.

modules/lang/org/autoload/org.el

@@ -149,15 +149,13 @@ If on a:
 
       (_ (+org/refresh-inline-images)))))
 
-;;;###autoload
-(defun +org/insert-item (direction)
+(defun +org-insert-item (direction)
   "Inserts a new heading, table cell or item, depending on the context.
 DIRECTION can be 'above or 'below.
 
 I use this instead of `org-insert-item' or `org-insert-heading' which are too
 opinionated and perform this simple task incorrectly (e.g. whitespace in the
 wrong places)."
-  (interactive)
   (let* ((context
           (save-excursion
             (when (bolp)
@@ -237,6 +235,18 @@ wrong places)."
     (when (bound-and-true-p evil-local-mode)
       (evil-insert 1))))
 
+;;;###autoload
+(defun +org/insert-item-below (count)
+  (interactive "p")
+  (dotimes (_ count)
+    (+org-insert-item 'below)))
+
+;;;###autoload
+(defun +org/insert-item-above (count)
+  (interactive "p")
+  (dotimes (_ count)
+    (+org-insert-item 'above)))
+
 ;;;###autoload
 (defun +org/dedent ()
   "TODO"