Feature 4148 New cryptographic function: a variation of SHA-512

To toughen the encryption of passwords, a new cryptographic algorithm is added: a variation of SHA-512 as used in the Unix systems.

Refactoring of the authentication classes used in the authentication mechanism: their name indicates what is their responsibility, clean up the code to be more comprehensible, move to the new package org.silverpeas.authentication. Only old codes for which I don't know if they are yet used are stayed in place in the old package com.stratelia.silverpeas.authentication.

Merge the code of Yohan from the Silverpeas master.

Don't forget to merge Silverpeas Component (same branch name)