Supports counter-based (i.e. HOTP security tokens) passwords for special usage

[torinkwok]

References:

• http://blogs.forgerock.org/petermajor/2014/02/one-time-passwords-hotp-and-totp
• https://tools.ietf.org/html/rfc2289
• https://tools.ietf.org/html/rfc6238#section-1.1
• https://en.wikipedia.org/wiki/HMAC-based_One-time_Password_Algorithm