WinRT: Readded QFileSystemEngine::id

Change-Id: I0729ecca6a615bbdb590f90d4257d17c4a10f11a
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Fixed crash in qeventdispatcher_winrt.cpp

The qthread autotest tried to Release the timerFactory before it was
initialized.

Change-Id: Ib7588632b9f48d56904632652e1a759595691e70
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Andrew Knight <andrew.knight@digia.com>