Fix various problems
This request fixes following problems:
- fix multithreading issues in Copy/Move/Delete/File properties
- fix cancelling copying/moving multiple files
- allow cancelling copying/moving/deleting single file
- fix displaying location/volume/free space in File properties for directories
- fix problems with creating new directories when samba support is enabled
- fix disabling all plugins
- add support for absolute paths in Shift+F4, Shift+F5 and Ctrl+Shift+F5
- focus on new file in Shift+F4
- other small bug fixes