TODO:
* add custom cronjob time
* add expert option to specify extra rsync arguments
* 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
