Enable to set and wipe the backup passphrase key

[HenriGEIST]

This pull request enable setting resetting the backup passphrase key containing the sha256sum of the passphrase.
This is done by adding the BACKUP name in the code like RSA1 to RSA2 and ECC1 to ECC16.

Then it is possible to set the passphrase with:

read -s -p "Enter Passphrase:" PASSPHRASE1
echo
read -s -p "Retype passphrase:" PASSPHRASE2
echo
if [ "$PASSPHRASE1" != "$PASSPHRASE2" ]
then
echo "Error passphrases mismatch" > /dev/stderr
else
onlykey-cli setkey BACKUP x b $(printf "%s" "$PASSPHRASE1" | sha256sum | grep -o '[0-9a-fA-F]*')
fi
PASSPHRASE1=""
PASSPHRASE2=""

And wipe it with:

onlykey-cli wipekey BACKUP