qmlviewer continues to use CPU cycles after startup animation has finished

Steps to reproduce:

• Launch qmlviewer, wait for the animation to finish
• Minimize/switch it to background
• Use 'top' to observe CPU consumption

Expected: qmlviewer process not using much CPU

Actual: qmlviewer stays at 4 - 6% CPU usage.

This seems to be caused by a rotating star image in startup.qml:

	loops: NumberAnimation.Infinite
	running: true

When the animation is finished, the (now invisible) star continues to rotate. This is bad for power consumption in mobile devices. Easy to fix, either use a finite number of loops for animating the star, or use 'running: Qt.application.active' to stop the animation when the app is in background.