init({activeTheme, locale} = {}) {
        // This function is called during theme initialization, and when switching language or theme.
        this._locale = locale || this._locale;
        this._activetheme = activeTheme || this._activetheme;

        super.init();
    }
Setup i18n support for themes:
 - Load correct language file into memory

@param {object} options
@param {String} options.activeTheme - name of the currently loaded theme
@param {String} options.locale - name of the currently loaded locale