PLT-1800 Load server side locale from the config.json (#3092)

* PLT-1800 Load server side locale from the config.json

* Add support for locales with country specifics

* Fix localization on served locale file as plain/text

webapp/sass/styles.scss

@@ -9,6 +9,7 @@
 @import '~perfect-scrollbar/dist/css/perfect-scrollbar.css';
 @import '~font-awesome/css/font-awesome.css';
 @import '~bootstrap-colorpicker/dist/css/bootstrap-colorpicker.css';
+@import '~react-select/dist/react-select.css';
 
 // styles.scss
 @import 'utils/module';