LTS minimization algorithm implemented

The minimization is performed using the strong bisimulation
equivalence concept (e.g. tau actions are treated like the regular
actions).

For now the user cannot really use it, since the minimization is
performed on a local Lts that doesn't go in the 'processes' table.
Moreover, verbose output is output on the shell.

These user-interface fixes will be addressed in future patches.
add 'clone' argument to process_ref_translate()

Before this commit the process_ref_translate() function always
cloned the LTS stored in the 'processes' table.

This is actually necessary (in the current code) only when the LTS
is used as a building block for another LTS (e.g.
ProcessRefNode::translate()).

In all the other cases the clone is not necessary or even not
desiderable. In the shell minimize command, as en example, we
want to minimize the LTS stored in the 'processes' table, and not
a clone of it.
minimization: hide debug output