Add option to control how non-printable OctetString variables are parsed

[edmocosta]

OctetString variables values are parsed as hex-string when the value contains non-printable characters (ISO control characters).
For example, the OID octet string value Value is: \u202C is parsed as 56:61:6c:75:65:20:69:73:3a:20:e2:80:ac.

It would be useful to provide an option to allow users decide if those values should be parsed as hex-string, or using the original value, replacing the invalid characters by some replacement char. For example, considering the replacement char is ?, the same string would be parsed as Value is: ???.