Backup warning for missing keys
Backup function now check if there are missing wallet/pool keys(payment.skey/stake.skey/cold.skey/cold.vkey) deleted either manually or by previous backup job and warn that backup is not complete. -X parameter added to less to prevent it from launching in an altscreen when displaying changelog. This to not overwrite saved screen by tput smcup. Goal is to restore the terminal screen on CNTools exit and still keep old terminal history.