The  rationale is  that the  Algo.spid that  gave processes  access to
their pid via their neighbors was a bit weird. Also, it makes the anonymity
of the algorithm more explicit: an access to the pid could appear anywhere
in the program, while now, the pid must be in state.t!

Now, if the  user needs the pid,  he must store it  explicitly in the
state via the initialization function.

To force that, I've changed the Register interface (and thus GenRegister)

The rationale is that:
- in lurette mode, they should be the same for all algos already
- in batch mode, action declarations are ignored anyway (except in custom mode)

Indeed,  the  generated  oracle  and daemons  were  not  syntactically
correct in such cases, e.g., if an action was named "I(p)".

also, use (back) the odoc make rule now the image has been updated

- do not hard-code the size of the graph in the ml files
- do not print the whole state of big graphs. Indeed, for graphs of
  10000 nodes, if we print the path (which is itself an array of size 10000)
  we obtain 100 000 000 variables, which is too much for the rif file.