Replace exist calls by isfolder and isfile

matlab/+gsa/monte_carlo_filtering.m

matlab/+gsa/run.m

matlab/+identification/get_perturbation_params_derivs.m

matlab/+mom/check_irf_matching_file.m

matlab/+mom/default_option_mom_values.m

matlab/+mom/run.m

matlab/+occbin/graph.m

matlab/aggregate.m

matlab/backward/checkdatabase.m

matlab/backward/shock_decomposition_backward.m

matlab/check_matlab_path.m

matlab/cherrypick.m

matlab/clear_persistent_variables.m

matlab/convergence_diagnostics/mcmc_diagnostics_core.m

matlab/default_option_values.m

matlab/dynare.m

matlab/erase_compiled_function.m

matlab/estimation/check_posterior_sampler_options.m

matlab/estimation/check_prior_analysis_data.m

matlab/estimation/delete_mh_history_files.m