MDL-57451 theme_boost: Add checkboxgroup class to checkbox input element

theme/boost/templates/core_form/element-advcheckbox-inline.mustache

@@ -7,7 +7,7 @@
         <input type="hidden" name="{{element.name}}" value="{{element.frozenvalue}}">
     {{/element.frozen}}
 {{/element.hardfrozen}}
-<input type="checkbox" name="{{element.name}}"
+<input type="checkbox" name="{{element.name}}" class="{{element.extraclasses}}"
     id="{{element.id}}"
     {{#element.selectedvalue}}
         value="{{element.selectedvalue}}"

theme/boost/templates/core_form/element-advcheckbox.mustache

@@ -18,6 +18,7 @@
         {{/element.hardfrozen}}
         <input type="checkbox"
             name="{{element.name}}"
+            class="{{element.extraclasses}}"
             {{#element.selectedvalue}}
                 value="{{element.selectedvalue}}"
             {{/element.selectedvalue}}

theme/boost/templates/core_form/element-checkbox-inline.mustache

@@ -4,7 +4,7 @@
         <input type="hidden" name="{{element.name}}" value="{{element.frozenvalue}}">
     {{/element.frozen}}
 {{/element.hardfrozen}}
-<input type="checkbox" name="{{element.name}}"
+<input type="checkbox" name="{{element.name}}" class="{{element.extraclasses}}"
     id="{{element.id}}"
     {{#element.value}}
         value="{{element.value}}"

theme/boost/templates/core_form/element-checkbox.mustache

@@ -15,6 +15,7 @@
         {{/element.hardfrozen}}
         <input type="checkbox"
             name="{{element.name}}"
+            class="{{element.extraclasses}}"
             {{#element.value}}
                 value="{{element.value}}"
             {{/element.value}}