Added modify_set_max_mag method to EvenlyDiscretizedMFD.
Added modify_set_max_mag method to EvenlyDiscretizedMFD.

ROB-Seismology/oq-hazardlib,ROB-Seismology/oq-hazardlib,ROB-Seismology/oq-hazardlib,ROB-Seismology/oq-hazardlib