Fixed performance issues related to selections and deleting of files:
- Don't connect to KDirLister::itemDeleted(const KFileItem&), but KDirLister::itemsDeleted(const KFileItemList&). Otherwise Dolphin is informed about each single file deletion instead of getting the deleted items as a list. Thanks to David Faure for the hint!
- DolphinViewContainer::updateStatusBar() can be expensive when a lot of files are selected, as the file size must get retrieved. Assure that fast calls for updateStatusBar() don't trigger a synchronous update, do the update after 300 ms where no further update has been triggered.
- Dolphin provides a list of file items when emitting the selectionChanged() signal. Collecting the file items is a quite expensive operation, so use the same approach as when updating the statusbar: only emit the selection changed signal when no change has been done within 300 ms. This improves the performance when doing huge selections a lot.
- Make updateStatusBar() a private method, the main window should not need to take care about updating the statusbar (this is done internally now by DolphinViewContainer).