LP#1528627 Proof of Concept "MasterKey" AuthProxy Module

LP#1528627 Proof of Concept "MasterKey" AuthProxy Module

This module allows a user with the "masterkey" password to login as
any other user in the system, similar to root-level "su" in Unix.

USE THIS CODE AND MODULE AT YOUR OWN RISK.

To set up:
- In opensrf.xml, set auth_proxy <enabled> to 'true' (if not already)
- In same file, uncomment the configuration section for MasterKey
  within the auth_proxy configuration area
- Set the <masterkey> to some super-secret value

This has been tested with OPAC logins, but should work with any logins
supported by AuthProxy.pm (e.g. staff logins should work, but may have
developed some bugs since last tested).

Signed-off-by: Dan Wells <dbw2@calvin.edu>