QmlProfiler: sending start profiling message

Will be used by the client to show status in the GUI.
When profiling is stopped, data is sent immediately,
therefore no "stop profiling" message.

Change-Id: Idd12069a9707296b87e305e8b3cbf8e324989a3f
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>