CComponentsWindow: add method to set background image in window classes

- setBodyBGImage() exists as member of base class CCDraw and had
 no visual effect in this class, because visibility of window container is disabled.
 This additional member overloads the original methode and is using functionality from
 window body object. Example for buildinfo added.

TODO:
- background behavior of embedded objects must be global adapted if a background image is used


Origin commit data
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Commit: e53f35d939
Author: Thilo Graf <dbt@novatux.de>
Date: 2017-12-23 (Sat, 23 Dec 2017)

Origin message was:
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CComponentsWindow: add method to set background image in window classes

- setBodyBGImage() exists as member of base class CCDraw and had
 no visual effect in this class, because visibility of window container is disabled.
 This additional member overloads the original methode and is using functionality from
 window body object. Example for buildinfo added.

TODO:
- background behavior of embedded objects must be global adapted if a background image is used

src/gui/components/cc_frm_window.h

@@ -3,7 +3,7 @@
 	Copyright (C) 2001 by Steffen Hehn 'McClean'
 
 	Classes for generic GUI-related components.
-	Copyright (C) 2012-2016, Thilo Graf 'dbt'
+	Copyright (C) 2012-2017, Thilo Graf 'dbt'
 
 	License: GPL
 
@@ -435,6 +435,12 @@ class CComponentsWindow : public CComponentsForm, CCHeaderTypes
 		* @note 	use addExitKey() if new exec key is required
 		*/
 		virtual void removeExitKeys(){getBodyObject()->removeExitKeys();}
+
+		/**
+		* Sets an image for window background.
+		* @note 	The assigned image is assigned into body object! Main container, header and footer will be not touched.
+		*/
+		bool setBodyBGImage(const std::string& image_path);
 };
 
 class CComponentsWindowMax : public CComponentsWindow