Extracted routines for reading stochasts parameters. Added check for invalid child element of a stochast definition, i.e. if a stochast with a standard deviation is expected, adding a variationcoefficient element will result in an error and vice versa. Related to Issue [WTI-1162] git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@9171 5a3db67b-de53-47b5-99c8-a1c30a6650e2