Remove the warning for Qt 4.7.0: The minimum version for Qt Creator is now Qt 4.7.4.

Instead, warn users that the QmlX plugins won't be compiled if QtDeclarative or QtQuick1 is missing.
(QtQuick1 isn't compiled by default on Qt 5).

Change-Id: Ib9713282ad3759045a6eb994da1a12aac5176910
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@nokia.com>