Doc: Details for Scene Graph profiler

There seems to be a demand for more details on the events shown in the
scene graph profiler. This change should handle that.

Change-Id: I1de95a7168d9af98d75c163bb10e56699895c7fc
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>
Doc: Input Events category in QML profiler timeline

Change-Id: Ia4f152e0e25cb21ad6302c1bf788faff1a84e573
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>