Added commands FS_COPY, FS_DUPLICATE and FS_INITIALIZE

The wireformat is extended with the command:
 92 #define   FS_COPY        28   /* copy a file or merge files */
 93 #define   FS_DUPLICATE   29   /* duplicate a disk image or copy a directory */
 94 #define   FS_INITIALIZE  30   /* initialize (e.g. free buffers and remove file locks) */
these are needed to support the new CBM commands in "cmd.h"
 49         CMD_INITIALIZE = FS_INITIALIZE,
 53         CMD_VALIDATE   = FS_CHKDSK,
 54         CMD_COPY       = FS_COPY,
 55         CMD_DUPLICATE  = FS_DUPLICATE,
 56         CMD_NEW        = FS_FORMAT,