Add user and session methods.

[0xWDG]

• Create a user with user.create
  Requires username, password, email

• Remove a user with user.remove
  2 options:

     1. Send's a email which the user need to confirm (self deleted)
     2. Done by a Administrator (no email)
  

• Login a user with user.login
  With username or userID or email and correct password
  Gives back a sID (Session ID)

• Resume with a user account via user.session or session.continue
  Resume with session-token.

  $server->setSessionTime("+1 month"); // 1 month valid session token, 
                                    // (if not renewed automatically)
  
  $server->setBindSessionToIP(false); // bind session to IP-Address.
                                   // [Note] IF TRUE and a user lost wifi
                                   // the session is invalidated!
  

• Create a custom session with session.create
  If you want to use a custom session ID sID

• Invalidate a session with session.invalidate user.logout
  If the user logs out.

• Reset a user password withuser.reset
  Sends a password reset link
  [Admin] Invalidates the user's password, and sends a password reset link.

• Activate a user withuser.activate
  Activates the user
  [Admin] Activates the user

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Administrator only.

• Invalidate all user sessions with session.admin(istration).invalidateAll
  Only possible for a Administrator

• Set user login on/off via user.admin(istration).loginEnabled

• Set user registration on/off via user.admin(istration).registerEnabled

• change a user status with user.admin(istration).status
  Like permission level (such as admin(istrator), mod(erator), user, activate(d), deactivate(d), ban account)
  Not sure about what next

[0xWDG]

See #16 for more information.