CHANGE: Allow customisation of skewness of normalised random number generator by the exponent parameter: 0 or 1 - even distribution; 2: normal distribution with slight skew (squared); 3: normal distribution with large skew (cubed); 4 normal distribution with recursion skew (squared); 5: normal distribution with recursion skew (cubed); 6 and above: normal distrubition with multiple recursion skew (cubed; these values produce so extreme a skew as may be of limited usefulness).
TODO: Allow these settings to be added to simuconf.tab to customise passenger generation.