Slightly larger slider size

When using tick marks we clip the slider at the bottom
in both mac and gtk style. Even on windows the handle
is too small so I will increase the default size a bit.

Change-Id: Ief2cab5f8c9edbc8c1966530a0c3b52234c30796
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>

src/styles/Desktop/SliderStyle.qml

@@ -46,8 +46,8 @@ PaddedStyle {
         elementType: "slider"
         sunken: control.pressed
         implicitWidth: 200
-        contentHeight: horizontal ? 20 : 200
-        contentWidth: horizontal ? 200 : 20
+        contentHeight: horizontal ? 22 : 200
+        contentWidth: horizontal ? 200 : 22
 
         maximum: control.maximumValue*100
         minimum: control.minimumValue*100