repo_management/defaults.py:
Add the basic defaults module, providing data that translates keywords
found in the 'desc' and 'files' files of a binary repository database to
those used in JSON files, representing the same data.

repo_management/convert.py:
Add the convert module, and introduce the simple private method
(reimplementing a subset of the features from db2json)
`_files_data_to_dict()`, which translates the contents of a `files` file
to a typed dict.