UP-4200 Decrypt password for portlets when replaying credentials

https://issues.jasig.org/browse/UP-4200

Only applies when using local login form to authenticate against DB or LDAP.
Since it's a commented-out-by-default bean, I'm fine with the commented-out configuration being one to pass the password as plaintext rather than encrypted, since an adopter un-commenting it is probably wanting that alas-more-common configuration.