Feature request: Status/progress indicator when deleting directories with large number of enclosed files.

[eriktier]

Current when deleting directories with many files the system seems to be frozen as their is no 'in progress' kind of indicator. With very long and 'deep' directory structures this can take a significant amount of time. It would be very nice if the UI would show a dialog indicating a delete is in progress (similar to the copying of files). After looking at: void TreeBrowser::delete_selected(void), I think this 'issue' is really caused by a very long counting of all the included files/subdirectories. I think by including the counting of the files as part of the progress indication this would be solved.