Added ApplicationStateChangeEvent handling to QQuickApplication.

Change-Id: I8b8965bc36b483be7287abf4485221f428a0b92a
Reviewed-by: Alan Alpert (Personal) <416365416c@gmail.com>
QtDeclarative: Removing parallel_test from config

tst_qquickvisualdatamodel and tst_qquickpositioners have been failing
recently on CI. One can't reproduce the failures locally unless
running the tests parallel, like CI does.

Task-number: QTQAINFRA-705
Change-Id: I09a9123d045f2213af915518917ce622b33b27ba
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>