Update locking state from external views and cleanup

Improve treeview styling related to locking/pinning
    Use font icons.
    Show implicitly locked nodes by darkening text and icon.
    Show implicitly locked curves by darkening the text.
    Show unlocked/unpined icons only when hovering the mouse above the item.
It is now possible to lock/pin multiple curves by locking/pinning the node items.
Load unselected curves into the graphicsview when pinning them.
Rename namespace DesignTools to QmlDesigner.
Remove unused function from the timeline module.
Get rid of a memory leak.

Change-Id: I2c9c0a9e1ffe79520c4869178a11cc5825d04bbe
Reviewed-by: Henning Gründl <henning.gruendl@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/components/curveeditor/animationcurve.cpp

@@ -33,7 +33,7 @@
 
 #include <sstream>
 
-namespace DesignTools {
+namespace QmlDesigner {
 
 AnimationCurve::AnimationCurve()
     : m_fromData(false)
@@ -395,4 +395,4 @@ void AnimationCurve::analyze()
     }
 }
 
-} // End namespace DesignTools.
+} // End namespace QmlDesigner.