WIP on an (optional) user management module.
Make session constructor private.

To make it clearer that this is an object who get one from the other classes, you don't usually create one yourself.
Add cryptopp library for the (optional) password module's hash function.
Remove cryptopp. Millions of files and can't make it build.
I think I accidentally a user account management.

The included accounts.txt file defines a user of class "owner" named "admin" with password "eleven".