Add support for pam_interactive auth plugin

[korydraughn]

See https://github.com/irods/irods_auth_plugin_pam_interactive

[d-w-moore]

Is #499 a prerequisite for this one?

[alanking]

Correct

[korydraughn]

@khansameer25 is the iRODS intern who implemented support for the PAM Interactive auth scheme in the PRC.

Closing.