QmlProfiler: Remover "rubber" behavior for horizontal Flickable.

By overflicking you could reduce the selected range and implicitly zoom
in. That seemed wrong. The rubber effect doesn't serve a real purpose
on desktop applications anyway.

Task-number: QTCREATORBUG-10864
Change-Id: Id4d6107e23c184621c5fcce21bf042e6ed4bd8e6
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Make range selection boundaries consistent

You shouldn't be able to select out of range areas with the selector in
the timeline if you can't scroll to see them anyway.

Change-Id: Ia1909f463db2c64dc2605eac7f4be53a76222338
Reviewed-by: Kai Koehne <kai.koehne@digia.com>