(1) add lattice_pce150 EOS
(2) change the IEOS to eos_type, which is more explicit
eos_type has the choices "ideal_gas", "first_order", "lattice_pce165",
"lattice_pce150", "lattice_wb", "pure_gauge".
(3) the default EoS is changed from lattice_pce165 to lattice_pce150,
which produces better pion/proton ratio if switching time is 155 MeV.