1. Added a signature() method to Mod1NumberIntExchange that can be used
to check that operators work only on compatible objects. For classes in
the scc folder, the foliation() method serves this purpose: only classes
with the same related Foliation make sense to work together. Some of
these compatibility checks are already made by asserts, some, especially
in the ssc folder still has to be done.

2. Added the Mod1NumberIntExWithInfo classes which is the container of a
Mod1NumberIntExchange and the smallContainingInterval of the Foliation
that contains it. It without remembering the index of this small
interval in this class, it would have to be calculated over and over in
different parts of the program.