QmlProfiler: eliminate redundant name() methods.

Change-Id: I6190fb1ba9fb86741362a251ddd3e39357b9a604
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: eliminate redundant isEmpty() methods

Change-Id: I05a82b0620a739d27478501ab43d2ac23839a811
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Make time formatting available to all timeline models

... and remove some dead code.

Change-Id: Ifdec932b87e8d33420d9713bfde9c4002f34844b
Reviewed-by: Kai Koehne <kai.koehne@digia.com>