Give a prefix and bindings for org applications

Related to syl20bnr#1296.

Use `SPC a o` as prefix for org related applications like `org-agenda`
or `org-capture`. The `a` is for "application", and `o` for "org". To
avoid long keystrokes for `agenda`, direct bindings are offered through
`SPC a o <key>`.

Because `org-agenda` is one of the principal application, it has be
mapped to repeating the last letter (`SPC a o o`).

(cherry picked from commit 2b5b2d3)

layers/org/README.org

@@ -12,6 +12,7 @@
    - [[#different-bullets][Different bullets]]
  - [[#key-bindings][Key bindings]]
    - [[#org][Org]]
+   - [[#org-with-evil-org-mode][Org with evil-org-mode]]
      - [[#tables][Tables]]
      - [[#tree-][Tree ]]
      - [[#element-insertion][Element insertion]]
@@ -75,6 +76,24 @@ You can tweak the bullets displayed in the org buffer in the function
 
 * Key bindings
 ** Org
+| Key Binding | Description                    |
+|-------------+--------------------------------|
+| ~SPC a o #~ | org agenda list stuck projects |
+| ~SPC a o /~ | org occur in agenda files      |
+| ~SPC a o a~ | org agenda list                |
+| ~SPC a o c~ | org capture                    |
+| ~SPC a o e~ | org store agenda views         |
+| ~SPC a o l~ | org store link                 |
+| ~SPC a o m~ | org tags view                  |
+| ~SPC a o o~ | org agenda                     |
+| ~SPC a o O~ | org clock out                  |
+| ~SPC a o s~ | org search view                |
+| ~SPC a o t~ | org todo list                  |
+| ~SPC C c~   | org-capture                    |
+| ~SPC C t~   | ort/capture-todo               |
+| ~SPC C T~   | ort/capture-checkitem          |
+
+** Org with evil-org-mode
 | Key Binding                                  | Description                                  |
 |----------------------------------------------+----------------------------------------------|
 | ~SPC m '~                                    | org-edit-special                             |
@@ -221,12 +240,9 @@ org-present must be activated explicitly by typing: ~SPC : org-present~
 | ~q~         | quit           |
 
 ** Org-repo-todo
-| Key Binding | Description           |
-|-------------+-----------------------|
-| ~SPC C c~   | org-capture           |
-| ~SPC C t~   | ort/capture-todo      |
-| ~SPC C T~   | ort/capture-checkitem |
-| ~SPC m g t~ | ort/goto-todos        |
+| Key Binding | Description    |
+|-------------+----------------|
+| ~SPC m g t~ | ort/goto-todos |
 
 ** Org-MIME
 | Key Binding | Description                                       |

layers/org/packages.el

@@ -65,6 +65,7 @@
 (defun org/init-org ()
   (use-package org
     :mode ("\\.org$" . org-mode)
+    :commands (org-clock-out org-occur-in-agenda-files)
     :defer t
     :init
     (progn
@@ -196,7 +197,24 @@ Will work on both org-mode and any mode that accepts plain html."
         (define-key org-agenda-mode-map
           (kbd "RET") 'org-agenda-show-and-scroll-up)
         (define-key org-agenda-mode-map
-          (kbd "SPC") evil-leader--default-map)))
+          (kbd "SPC") evil-leader--default-map))
+
+      ;; Add global evil-leader mappings. Used to access org-agenda
+      ;; functionalities – and a few others commands – from any other mode.
+      (evil-leader/set-key
+        ;; org-agenda
+        "ao#" 'org-agenda-list-stuck-projects
+        "ao/" 'org-occur-in-agenda-files
+        "aoa" 'org-agenda-list
+        "aoe" 'org-store-agenda-views
+        "aom" 'org-tags-view
+        "aoo" 'org-agenda
+        "aos" 'org-search-view
+        "aot" 'org-todo-list
+        ;; other
+        "aoO" 'org-clock-out
+        "aoc" 'org-capture
+        "aol" 'org-store-link))
     :config
     (progn
       ;; setup org directory