fdo#72187 Implement KDE4 picker notifications

This notifies the XFilePickerListener of filter changes and file
selection changes.

Change-Id: I749c5f7420f020a3a2fbb764acb5c45d40972cf1
(cherry picked from commit a8d102c2406b8c027afb32d61271e0a2c301f133)
Reviewed-on: https://gerrit.libreoffice.org/7907
Tested-by: Michael Stahl <mstahl@redhat.com>
Reviewed-by: Michael Stahl <mstahl@redhat.com>