TODO:
* add option to preserve permissions (snapshots will no longer be read-only)
* add expert option to specify extra rsync arguments
* allow include directories to mix with snapshots directory (but exlude snapshots directory)
* refresh button should force files view update too
* add "expert option": cron take snapshot command template (default: "nice 19 %s >/dev/null 2>&1")
* use rsync return code to check that the snapshot was really taken (no out of space, copy error ...)
* Toolbars: add different texts for labels and tooltips
* KDE4: handle command line parameters
* KDE4: handle application raise
* KDE4: add right-click menu
* KDE4: better integration with kde/dolphin
