Read and return Nastran op2 matrix at current file position.
It is assumed that the name has already been read in via rdop2nt().
rdop2nt()
rows = trailer[2] cols = trailer[1]
OP2.rdop2matrix()
pyyeti.nastran.op2.OP2.rdop2gpwg
pyyeti.nastran.op2.OP2.rdop2mats