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/buildinfo.cpp

@@ -3,7 +3,7 @@
 	Copyright (C) 2001 by Steffen Hehn 'McClean'
 
 	Copyright (C) 2013, M. Liebmann 'micha-bbg'
-	Copyright (C) 2013-2014, Thilo Graf 'dbt'
+	Copyright (C) 2013-2017, Thilo Graf 'dbt'
 
 	License: GPL
 
@@ -40,6 +40,7 @@ using namespace std;
 CBuildInfo::CBuildInfo(bool show) : CComponentsWindow(0, 0, CCW_PERCENT 85, CCW_PERCENT 85, LOCALE_BUILDINFO_MENU, NEUTRINO_ICON_INFO)
 {
 	initVarBuildInfo();
+	setBodyBGImage(DATADIR "/neutrino/icons/start.jpg");
 	if (show)
 		exec(NULL, "");
 	else