Fix BlackBerryConfigurationManager singleton

The usage of a static variable instead of a pointer guarantees it will be
constructed and destructed only once.

Change-Id: I7f587ec131b43fe5685122e9a384f1871dcdf790
Reviewed-by: Mehdi Fekari <mfekari@blackberry.com>
Reviewed-by: David Kaspar <dkaspar@blackberry.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>