Offline OTP with privacyIDEA

Check this out!

The latest commit added offline functionality to the PAM module of
privacyIDEA

When the user successfully authenticates with his OTP token against
privacyIDEA (and the MachineToken def is defined), the server returns a
bunch of hashed OTP values.
These are stored on the client side in an sqlite database enabling
offline (and still online) authentication with the e.g. notebook.

This is an early working proof of concept.
There are some things to polish and then it will be released as version 2.2!

Kind regards
Cornelius