rework backup.sh order

[Lex-2008]

• "old files" should be done before "new files" - to decrease "for_update" index

• "old files" should work in one pipeline: sqlite query should both update DB and produce output for file operations - like backup1.sh does

• maybe increase pipe size
  https://unix.stackexchange.com/questions/439196/change-buffer-size-of-named-pipe