add parthenon/output# to src/parthenon_params.yaml

[smao-astro]

May I ask for adding the parthenon/output input parameters to src/parthenon_params.yaml? For example, we might have the parameters below in input file

<parthenon/output1>
variables = gas.prim.density,  &
            gas.prim.velocity, &
            gas.prim.pressure
file_type = hdf5               # HDF5 data dump
dt        = 6.283185307179586  # time increment between outputs

<parthenon/output2>
file_type = rst                # Restart
dt        = 6.283185307179586  # time increment between outputs