add IntervalOfContainers which are described in https://gforge.inria.fr/plugins/wiki/index.php?NewDataStructPage&id=1596&type=g
A new IntervalOfContainer is built only when a certain (10000 for the moment) number of StateChanges or Links are attached to it. (initially only StateChanges were taken into account, but Links are created in parent containers without States, so they were all allocated in the same IntevalOfContainers, making them huge).

This is not activated right now by default, but can be turned on by setting the flag USE_ITC before compiling to perform tests.