vectorized cdf and use operands_and_partials for exp_mod_normal distr
added cdf_log to exp_mod_normal
added operands_and_partials to gumbel cdf
added cdf_log to gumbel distribution
added cdf_log to inv_chi_square distr
added cdf_log to inv_gamma distr
added cdf_log to logistic distr
added operands_and_partials to cdf for lognormal
added cdf_log to lognormal distr