Open correct detault folder when the use decides to reuse a existing private key file

When adding a new BlackBerry device, esp, another version of the simulator, users might wish to reuse existing private keys which have been generated to already configured devices. The QFileDialog opens with the current folder and not with the folder where private keys are usually stored. It VERY hard to find the right location of the keys w/o insider knowledge where QtCreator stores files. Please open the correct folder!