The previous  scheme was to  define everything  that is common  to all
user nodes in  a file named state.ml. This file was supposed to define
the algo  state type,  as well  as optional  functions such  as fault,
legitimate, or potential.

But in  order to be  able to define,  say, a legitimate  function that
uses user  nodes (which is the  case for dijkstra token  ring) without
introducing any dependency loop, it  is necessary to split state.ml in
two modules.

The new module is called Config (config.ml).

nb: I had to modify the GenSessions module in rdbg to reflect this change !

Update: add the potential value of the current state as an output of sasa programs in the rdbg plugin
if the potentioal function is provided

Doc: mention the new rdbgui4sasa opam package

Build: split the sasa opma package to separate it fron rdbgui4sasa (and remove a dependancy on gtk3)

also, start the first step at 0  instead of 1. Otherwise, with -cd, we
get more  steps than  moves. Indeed,  the first step  is not  really a
step; it just contain the initial state values.

It now takes  as first argument the whole list  of processes (not only
the enabled ones).

In  Algo.pf_info, the  action  field  is now  an  option  type (if  is
correspond to a process that has not been activated).

nb: does not really work yet.

Update: add the previous state in argument of the fault function.

New: add a fault functions to the Algo (to inject fault when a legitimate configuratiuon is reached).

nb: I needed to  split Main to avoid a Module self-loop  (as I need to
use do_step in Daemon).