update 31/9

major changes:
- improved xbrick integration subroutine:
new elem status : elfailm and elfailf for matrix induced failure
partition and fibre induced failure partition
- elfailm can be caused by edge status update and matrix failure
criterion
- elfailf can only be caused by fibre failure criterion on intact elem
- fibre failure is only allowed in two cases: fibre induced failure
partition and matrix induced failure partition after coh sub elem has
started to fail
minor changes:
- moved elem stat values from param module to respective elem modules
- made public lamina failure status variable values
- fibre cohesive law back to old one: degradation and onset can be
performed within the same iteration (avoid stress overshoot at the
expense of disp. jump)