Darken menu border color

The lightgray menu border color #ededed introduced in
commit f147e5a66f (by PR #2095)
is way too light for my display (and probably others).
Thus the menus have no clear border which looks odd and broken.

This commit simply darkens the menu border to #bdbdbd, which
coincides with the (current default) color of the menu separator.

Signed-off-by: Stephan Beyer <s-beyer@gmx.net>

theme/Style/Style.qml

@@ -8,7 +8,7 @@ QtObject {
     property color ncBlue:      "#0082c9"
     property color ncBlueHover: "#009dd9"
     property color lightHover:  "#f7f7f7"
-    property color menuBorder:  "#ededed"
+    property color menuBorder:  "#bdbdbd"
 
     // Fonts
     // We are using pixel size because this is cross platform comparable, point size isn't