QmlProfiler: Remove dead code

No need to keep properties around that aren't read anywhere.

Change-Id: Ie9300ad646466a6a2368f644a420d8654891805f
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: When clearing, set the trace duration to 0

That is what the code in the main view expects of an empty trace and
it's also logically more coherent.

Task-number: QTCREATORBUG-11833
Change-Id: I78b90ca5332bfb004cabbb32c4eb3e7e83fd7187
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Consistently clear when clear button pressed

Several QML properties need extra treatment to avoid stale data
after clearing. Toggling the visibility of the timeline renderer
doesn't really help there.

Task-number: QTCREATORBUG-11833

Change-Id: I1903d7bd69d6fe31ecc4cadca8e30fa2104fa09a
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Show a trace duration of 0 while data is being cleared

Task-number: QTCREATORBUG-11834
Change-Id: Ie93ee7ed79534e86feec5809ef8e91a74da380fa
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Apply some coding style

Change-Id: I34d74254cf677c14538d937a596ff72054f89300
Reviewed-by: Kai Koehne <kai.koehne@digia.com>