QQuickSystemPalette: use QGuiApplication::paletteChanged()

Use the newly introduced signal instead of filtering events
of the whole application.

Change-Id: I876268145485ba07316e916d26a93d53c464ef3a
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Tools and examples: consistently use organization name QtProject

This affects the location of the QSettings files or registry entries.
Other parts of Qt are using this organization name so it's good to
have all the settings in the same place.

[ChangeLog][QtQuick] tools and examples consistently use the
QtProject organization name

Change-Id: I1fae4eaed0248411fe95dda9572d38006648b162
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>