Timeline: Make all the colors in the selection range alpha blended

Changing an item from alpha blended to solid or vice versa forces a
full rebuild. The difference between solid and 0xfe alpha won't be
visible.

Change-Id: I4da47870fc465449f0354a18fc87717c569be812
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

src/libs/timeline/qml/RangeMover.qml

@@ -35,12 +35,12 @@ Item {
     anchors.fill: parent
     signal rangeDoubleClicked()
 
-    property color handleColor: "#869cd1"
+    property color handleColor: "#fe869cd1"
     property color rangeColor:"#444a64b8"
     property color dragColor:"#664a64b8"
     property color borderColor:"#cc4a64b8"
-    property color dragMarkerColor: "#4a64b8"
-    property color singleLineColor: "#4a64b8"
+    property color dragMarkerColor: "#fe4a64b8"
+    property color singleLineColor: "#fe4a64b8"
 
     property alias rangeLeft: leftRange.x
     property alias rangeRight: rightRange.x