Introduce general.el & rewrite map!

+ Now uses an overriding keymap for leader keys, so that it is always
  available, even outside of normal/visual states. In insert/emacs
  states, or in sessions where evil is absent, an alternative prefix is
  used for leader/localleader keys. See these variables:
  + doom-leader-prefix
  + doom-leader-alt-prefix
  + doom-localleader-prefix
  + doom-localleader-alt-prefix
+ Keybinds now support alternative prefixes through the new :alt-prefix
  property. This is useful for non-evil users and non-normal evil
  states. By default, this is M-SPC (leader) and M-SPC m (localleader).
+ Removed +evil-commands flag from config/default (moved to
  feature/evil/+commands.el).
+ config/default/+bindings.el has been split into
  config/default/+{evil,emacs}-bindings.el, which one is loaded depends
  on whether evil is present or not. The latter is blank, but will soon
  be populated with a keybinding scheme for non-evil users (perhaps
  inspired by #641).
+ The define-key! macro has been replaced; it is now an alias for
  general-def.
+ Added unmap! as an alias for general-unbind.
+ The following modifier key conventions are now enforced for
  consistency, across all OSes:
    alt/option      = meta
    windows/command = super
  It used to be
    alt/option      = alt
    windows/command = meta
  Many of the default keybinds have been updated to reflect this switch,
  but it is likely to affect personal meta/super keybinds!

The map! macro has also been rewritten to use general-define-key. Here
is what has been changed:

+ map! no longer works with characters, e.g. (map! ?x #'do-something) is
  no longer supported. Keys must be kbd-able strings like "C-c x" or
  vectors like [?C-c ?x].
+ The :map and :map* properties are now the same thing. If specified
  keymaps aren't defined when binding keys, it is automatically
  deferred.
+ The way you bind local keybinds has changed:

    ;; Don't do this
    (map! :l "a" #'func-a
          :l "b" #'func-b)
    ;; Do this
    (map! :map 'local "a" #'func-a
                      "b" #'func-b)

+ map! now supports the following new blocks:
  + (:if COND THEN-FORM ELSE-FORM...)
  + (:alt-prefix PREFIX KEYS...) -- this prefix will be used for
    non-normal evil states. Equivalent to :non-normal-prefix in general.
+ The way you declare a which-key label for a prefix key has changed:

    ;; before
    (map! :desc "label" :prefix "a" ...)
    ;; now
    (map! :prefix ("a" . "label") ...)

+ It used to be that map! supported binding a key to a key sequence,
  like so:

    (map! "a" [?x])  ; pressing a is like pressing x

  This functionality was removed *temporarily* while I figure out the
  implementation.

Addresses: #448, #814, #860
Mentioned in: #940

modules/tools/ein/config.el

@@ -37,6 +37,7 @@
     (string-match-p "^\\*ein: .*" (buffer-name buf)))
   (add-to-list 'doom-real-buffer-functions #'+ein-buffer-p nil #'eq)
 
-  ;; Ace-link on notebook list buffers
-  (after! ein-notebooklist
-    (define-key ein:notebooklist-mode-map "o" #'+ein/ace-link-ein)))
+  (map! :map ein:notebook-mode-map
+        "M-s" #'ein:notebook-save-notebook-command
+        :map ein:notebooklist-mode-map
+        "o" #'+ein/ace-link-ein))

modules/tools/magit/config.el

@@ -45,12 +45,7 @@ what features are available.")
     #'hide-mode-line-mode)
 
   ;; properly kill leftover magit buffers on quit
-  (define-key magit-status-mode-map [remap magit-mode-bury-buffer] #'+magit/quit)
-
-  ;; Don't replace the leader key
-  ;; FIXME remove me when general.el is integrated
-  (when doom-leader-key
-    (define-key magit-diff-mode-map (kbd doom-leader-key) nil)))
+  (define-key magit-status-mode-map [remap magit-mode-bury-buffer] #'+magit/quit))
 
 
 (def-package! magit-todos
@@ -94,11 +89,7 @@ what features are available.")
   (setq evil-magit-state 'normal
         evil-magit-use-z-for-folds t)
   :config
-  (define-key! magit-mode-map ; replaced by z1, z2, z3, etc
-    (kbd "M-1") nil
-    (kbd "M-2") nil
-    (kbd "M-3") nil
-    (kbd "M-4") nil)
+  (unmap! magit-mode-map "M-1" "M-2" "M-3" "M-4") ; replaced by z1, z2, z3, etc
   (evil-define-key* '(normal visual) magit-mode-map
     "zz" #'evil-scroll-line-to-center
     "%"  #'magit-gitflow-popup)
@@ -108,6 +99,4 @@ what features are available.")
               (cdr key)))
     (evil-define-key* evil-magit-state git-rebase-mode-map
       "gj" #'git-rebase-move-line-down
-      "gk" #'git-rebase-move-line-up))
-  (define-key! (magit-mode-map magit-blame-read-only-mode-map)
-    (kbd doom-leader-key) nil))
+      "gk" #'git-rebase-move-line-up)))