problems found and fixed

- previously, subxcoh elem sdv stores the maximum of runtime igpoint sdv
array (sdv(2)) fstat and dm values; this is not correct, now it stores
max of converged sdv array (sdv(1)) fstat and dm values

- prevously, elem curr status values stores the maximum of all itrations
which may overshoot the actual status value; now they're zeroed and then
re-valued at each iteration, they store the max values of ig points
during that iteration; no max operation btw iterations is performed.

- add nofailure variable to coh, subxcoh to suppress damage modelling
during the iteration of new partition for xcoh elem

- improved interface ddsdde subroutine, made jump and stress compulsory
inputs, so that it can do linear elasticity in case sdv array is not
passed in.