Input data formats

[damonge]

We need to agree on data formats for the input data. A probably incomplete list of data whose format we need to agree on is:

• Maps: are we fine with fits files with either WCS images or healpix tables? Should we put all splits for the same band in the same file? Or create separate files per split? If the former, should all splits be in the same HDU or different HDUs.
• Bandpasses: something better than ASCII files would be desirable. Will we assume one bandpass file per band? Do we need separate bandpasses for diferent splits?
• Beams: same as above
• Transfer functions: before anything, we should probably figure out whether these are inputs or something we need to compute within the pipeline.
• Point source lists: for masking. What is the preferred format for these?