Fix login library (issue #5)
This version introduces multiple enhancements:

Rebuild some part of log_class, added possibility to use $_SESSION or session class.
Also fixed problem with regeneration of session id.

Details of additions/deletions below:
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Modified:   /BLUE_FRAMEWORK/packages/user/log_class.php
            -- Modified --
               logOn saving session id in session, $_SESSION replaced by self::setSessionVar
               logOff removing variables depends of model type
               verifyUser $_SESSION replaced by self::getSessionVar, added setting session id in session
               _code added usage of HTTP_ACCEPT_LANGUAGE, fixed usage of session id
            -- Added --
               SESSION_ARRAY const with name of session model when usage $_SESSION
               SESSION_CLASS const with name of session model when usage session class
               $_sessionModel variable to save set up session model
               setSessionModel to set proper session model
               getSessionVar to get proper session variable from model
               setSessionVar to set proper session variable from model
               _checkModelType to check type of given model