Use msDS-UserPasswordExpiryTimeComputed in the ActiveDirectoryAuthenticationResponseHandler

[dfish3r]

The msDS-UserPasswordExpiryTimeComputed attribute removes the need to compute expiration date.
It also appears to be an attribute that an authenticated user would have read access to.

[dfish3r]

@tduehr I changed my mind on allow authentication response handlers in the AD schema. Someone convinced me that these attributes are available to the user in some common configurations.

[tduehr]

I use FreeIPA, is this in response to the discussion on #62?

[dfish3r]

Yes. I reversed my position here: #62 (comment)