FIX: select-kit refactoring

- improve mini-tag-chooser keyboard behavior
- all multil select now respond to select all and left/right arrows
- improve events handling
- many minor tweaks

app/assets/javascripts/select-kit/components/admin-agree-flag-dropdown.js.es6

@@ -10,7 +10,7 @@ export default DropdownSelectBox.extend({
   headerIcon: "thumbs-o-up",
 
   computeHeaderContent() {
-    let content = this.baseHeaderComputedContent();
+    let content = this._super();
     content.name = `${I18n.t("admin.flags.agree")}...`;
     return content;
   },