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/completion/helm/config.el

@@ -34,25 +34,25 @@ be negative.")
 ;; Packages
 
 (def-package! helm-mode
-  :defer 1
+  :defer t
   :after-call pre-command-hook
   :init
-  (define-key! 'global
-    [remap apropos]                   #'helm-apropos
-    [remap find-library]              #'helm-locate-library
-    [remap bookmark-jump]             #'helm-bookmarks
-    [remap execute-extended-command]  #'helm-M-x
-    [remap find-file]                 #'helm-find-files
-    [remap imenu-anywhere]            #'helm-imenu-anywhere
-    [remap imenu]                     #'helm-semantic-or-imenu
-    [remap noop-show-kill-ring]       #'helm-show-kill-ring
-    [remap persp-switch-to-buffer]    #'+helm/workspace-mini
-    [remap switch-to-buffer]          #'helm-buffers-list
-    [remap projectile-find-file]      #'+helm/projectile-find-file
-    [remap projectile-recentf]        #'helm-projectile-recentf
-    [remap projectile-switch-project] #'helm-projectile-switch-project
-    [remap projectile-switch-to-buffer] #'helm-projectile-switch-to-buffer
-    [remap recentf-open-files]        #'helm-recentf)
+  (map! [remap apropos]                   #'helm-apropos
+        [remap find-library]              #'helm-locate-library
+        [remap bookmark-jump]             #'helm-bookmarks
+        [remap execute-extended-command]  #'helm-M-x
+        [remap find-file]                 #'helm-find-files
+        [remap imenu-anywhere]            #'helm-imenu-anywhere
+        [remap imenu]                     #'helm-semantic-or-imenu
+        [remap noop-show-kill-ring]       #'helm-show-kill-ring
+        [remap persp-switch-to-buffer]    #'+helm/workspace-mini
+        [remap switch-to-buffer]          #'helm-buffers-list
+        [remap projectile-find-file]      #'+helm/projectile-find-file
+        [remap projectile-recentf]        #'helm-projectile-recentf
+        [remap projectile-switch-project] #'helm-projectile-switch-project
+        [remap projectile-switch-to-buffer] #'helm-projectile-switch-to-buffer
+        [remap recentf-open-files]        #'helm-recentf
+        [remap yank-pop]                  #'helm-show-kill-ring)
   :config
   (helm-mode +1)
   ;; helm is too heavy for `find-file-at-point'
@@ -179,4 +179,5 @@ be negative.")
 (after! swiper-helm
   (setq swiper-helm-display-function
         (lambda (buf &optional _resume) (pop-to-buffer buf)))
+  (global-set-key [remap swiper] #'swiper-helm)
   (add-to-list 'swiper-font-lock-exclude #'+doom-dashboard-mode nil #'eq))