Squashed commit of the following:

commit 557df5cc5e62fab80125d1ea86f8ed56ad3b10cc
Author: Thomas Mueller <thomas.mueller@tmit.eu>
Date:   Fri Jun 28 15:17:54 2013 +0200

    session_life_time -> session_lifetime
    default session_lifetime is 24hrs
    recreation of session is triggered at 50% of the session life time

    Conflicts:
    	lib/base.php

commit fcd2e91459ef2ff41d9ca3d07e325c358ded091a
Author: Thomas Mueller <thomas.mueller@tmit.eu>
Date:   Wed Jun 26 09:19:19 2013 +0200

    session life time is now configurable and set to the same value

    Conflicts:
    	lib/base.php