MDL-66874 core: Allow master button checkbox toggle to be customisable

* Plus, add labelclasses data for template context in master and slave
checkbox templates.

lib/classes/output/checkbox_toggleall.php

@@ -60,7 +60,9 @@ class checkbox_toggleall implements renderable, templatable {
      *     <ul>
      *         <li><b>id          </b> string - The element ID.</li>
      *         <li><b>name        </b> string - The element name.</li>
-     *         <li><b>classes     </b> string - CSS classes that you want to add for your checkbox.</li>
+     *         <li><b>classes     </b> string - CSS classes that you want to add for your checkbox or toggle controls.
+     *                                          For button type master toggle controls, this could be any Bootstrap 4 btn classes
+     *                                          that you might want to add. Defaults to "btn-secondary".</li>
      *         <li><b>value       </b> string|int - The element's value.</li>
      *         <li><b>checked     </b> boolean - Whether to render this initially as checked.</li>
      *         <li><b>label       </b> string - The label for the checkbox element.</li>

lib/templates/checkbox-toggleall-master-button.mustache

@@ -31,12 +31,12 @@
         "togglegroup": "toggle-group",
         "label": "Select everything!",
         "checked": true,
-        "classes": "p-1",
+        "classes": "btn-primary btn-lg",
         "selectall": "Select all",
         "deselectall": "Deselect all"
     }
 }}
-<button type="button" id="{{id}}" name="{{name}}" class="btn btn-secondary {{classes}}"
+<button type="button" id="{{id}}" name="{{name}}" class="btn {{^classes}}btn-secondary{{/classes}}{{#classes}}{{.}}{{/classes}}"
         data-action="toggle"
         data-toggle="master"
         data-togglegroup="{{togglegroup}}"

lib/templates/checkbox-toggleall-master.mustache

@@ -33,7 +33,8 @@
         "checked": true,
         "classes": "p-1",
         "selectall": "Select all",
-        "deselectall": "Deselect all"
+        "deselectall": "Deselect all",
+        "labelclasses": "badge badge-info"
     }
 }}
 <input id="{{id}}" name="{{name}}" type="checkbox" {{#classes}}class="{{.}}"{{/classes}} value="{{value}}"

lib/templates/checkbox-toggleall-slave.mustache

@@ -31,7 +31,8 @@
         "togglegroup": "toggle-group",
         "label": "Select me!",
         "checked": true,
-        "classes": "p-1"
+        "classes": "p-1",
+        "labelclasses": "badge badge-info"
     }
 }}
 <input id="{{id}}" name="{{name}}" type="checkbox" {{#classes}}class="{{.}}"{{/classes}} value="{{value}}"