U2F login for SSH

In case of offline usage there is the possibility for SQL
injections

This enables to use passthru policy within the PAM stack.
A user with a token will be asked for the additional OTP value,
while a user without token can login with a simple password.

Working on #233

The extensions like .py and .sh were removed from
the scripts for comply with debian packaging rules.

Also fixed some hyphens/minus in man pages

Closes #232

for offline authentication

OR pam_unix.

Closes #116

Working on #116