Update HDF5 output for test image data with the correct file structure

[mdschneider]

The galsim_galaxy.py module contains our galaxy image model. If run as a command-line script it generates some test data for us to look at and use as simple inputs to Roaster.py.

The output HDF5 file saved in galsim_galaxy.py here needs to be updated to match the actual formats that @wadawson is designing for handling blended groups with multiple epochs/instruments.

We can then continue to use this functionality to make Roaster inputs that are generated with the same model as used to fit the data - the simplest possible test in some ways.

[mdschneider]

In addition to the parameters from a preliminary source extraction algorithm, the HDF5 file structure for multi-epoch blend groups needs to include some meta-information for simulating images:

• pixel scale
• wavelength or pass-band
• telescope name or, e.g., primary mirror diameter for choosing an Airy disk PSF
• whether to include an atmosphere PSF model