Do not fail if preprocessor-generated directories have already been removed (e.g. when only regenerating the tables)

Also do not duplicate stack_solve_algo values, rather pass them as an argument.

By the way:
– no longer hardcode unavailable algorithms in the LaTeX templates, but
  rather handle them with a special value (-10) as for the other types of
  failures
– no longer hardcode the possible values of stack_solve_algo in
  run_simulations.m, but rather use the vector of values passed as argument

If niter is negative, the number of iterations is abs(niter) but we
report the total time of simulation instead of the average
time (across iterations). This is useful if the benchmarked model is
small (and the simulation time below one second).

 - "crash" is for a code error,
 - "CRASH" is for a matlab crash (closing unexpectedly).

 - Add tex, pdf, png to be included in the README
 - Add matlab routine to produce the tables
 - Add template for short table (without solve_algo=7)

(cherry picked from commit 57f2efad1d6181ba18b189da75d34d85ff7acd80)