also use shadow color in Breeze style

kstyle/breeze.kcfg

@@ -21,6 +21,10 @@
        <max>64</max>
     </entry>
 
+    <entry name="ShadowColor" type = "Color">
+       <default>0, 0, 0</default>
+    </entry>
+
     <!-- close button -->
     <entry name="OutlineCloseButton" type = "Bool">
         <default>true</default>

kstyle/breezeshadowhelper.cpp

@@ -149,7 +149,7 @@ namespace Breeze
         {
 
             const QPalette palette( QApplication::palette() );
-            const QColor shadowColor( palette.color( QPalette::Shadow ) );
+            const QColor shadowColor( StyleConfigData::shadowColor() );
 
             // metrics
             const int shadowSize = StyleConfigData::shadowSize()*12/16;