Data Objects

[robertdstein]

This is a big breaking change that abolishes the lists-of-lists-of-lists nesting and introduces a clear, concrete data model for the processors.

There are now:

Data objects. These are either Image or SourceList objects. These replace a tuple image/header and pandas dataframe everywhere.

Batch objects. These are either ImageBatch or SourceBatch objects. They replace "batch" lists.

DataSet objects. These replace the list-of-batches. They must contain batches of the same type.

Bonus: Introduce the concept of metadata for SourceList, so you can assign in a dictionary-like way values to the SourceList rather than adding a column to all individual rows. You can then e.g batch these etc.