[CONUTILS] Diverse improvements: start doxygenating and add some resource messsage helper functions.

- Start to doxygenate the library, focusing in great details on the
  functions of the "outstream" module.
- Add a K32LoadStringEx function that expands (K32)LoadString by
  allowing a LanguageId parameter to be able to load strings from other
  languages than the current one.
- Add "ConResMsg*" helper functions to be able to (format and) print
  message strings with inserts that come *NOT* from a message table (as
  usual) *BUT* from resource string tables.
  Will be helpful for CORE-14265 in particular.

[CMD] Fix the call to ConMsgPrintfV().

sdk/lib/conutils/conutils.h

@@ -8,6 +8,21 @@
  *              Copyright 2017-2018 Hermes Belusca-Maito
  */
 
+/**
+ * @file    conutils.h
+ * @ingroup ConUtils
+ *
+ * @defgroup ConUtils   ReactOS Console Utilities Library
+ *
+ * @brief   This library contains common functions used in many places inside
+ *          the ReactOS console utilities and the ReactOS Command-Line Interpreter.
+ *          Most of these functions are related with internationalisation and
+ *          the problem of correctly displaying Unicode text on the console.
+ *          Besides those, helpful functions for retrieving strings and messages
+ *          from application resources are provided, together with printf-like
+ *          functionality.
+ **/
+
 #ifndef __CONUTILS_H__
 #define __CONUTILS_H__