PeaZip 3.2.1

* BACKEND
- (Windows) 7z 9.15 beta
* FILE MANAGER
- fixed browsing some types of split compressed files, i.e. .bz.001
- fixed preserving/removing original file extension in archive name accordingly to archive type
- added optional theming image for file manager's toolbar
* WINDOWS INSTALLER
- fixed: the installer now removes older versions' language files during the installation
* LINUX INSTALLERS
- Nautilus script files are now marked as executable, as required in some distributions
- (Qt version) the installer now tries to link libqt4intf.so in some more paths used by some distributions