Changing DSPSPhotometryCreator output format

[torluca]

The idea is to change the DSPSPhotometryCreator output from an Hdf5Handle to a format that can be read by Pandas. Reason being we want to chain it to LSSTErrorModel.

[torluca]

We also found another problem. When parallelizing rail_dsps according to the example in estimator.py, if we try to run a pipeline with ceci, it does not work and does not produce any output, neither on the laptop nor on NERSC. If we run the stage on a Jupyter notebook, it works flawlessly