Behaviour changes:
- "Move to trash" option in context menu only if trashing is possible
- DEL_Key, F11 or "Move to trash" option now moves files to trash on virtual
FS (if possible for all selected files)
Panel: rework of ListPanelFunc::deleteFiles()
And vfs::deleteFiles() expects the final decision for "moveToTrash" argument now!
Panel: Move files to trash if this is possible and activated in user settings
Else, fallback to real deletion.
It is now possible to move virtual files to trash.
Moved code for deciding if files can be moved to trash to VFS
Panel: show trash option in right-click popup menu only if trashing is supported
VFS: separate virtual deletion and real/trash deletion in virtual vfs.
And call appropriate method in panel.
VFS: merged common code for deleting/trashing files in vfs subclasses into superclass
Panel: split code for deleting/trashing files and removing virtual files