QNX: Adding native file dialog support for Blackberry

QNX: Adding native file dialog support for Blackberry

This patch enables use of native file dialogs in the application
modal case.

The native file open dialog is reasonable but the native file save
dialog could do with some improvements to make it more usable.
Perhaps providing our own "native" dialog UI would be an option
once the widget style is finished.

Change-Id: If5fb7cf73d27e52db7bfa6d97d8f8fb7912960bb
Reviewed-by: Nicolas Arnaud-Cormos <nicolas@kdab.com>