First pass as expand operation

[beckyjackson]

Resolves #98

expand

The expand module takes an import table and creates an explicit import table that contains all terms that will be in the extracted module and the reason that they are included. The reason will be one of: ancestor, child, descendant, or parent of an included term.

python3 -m gizmos.expand -d [path-to-database] -i [import-table] > [output-tsv]

The default output format is TSV, but if you want to write a CSV, you can include -f csv/--format csv.

By default for each reason, up to three terms are included (e.g. if a term is a descendant of included terms X, Y, Z). When the term is related to more than three terms, the reason will be shown as "descendant of N terms", where N is the number of terms. You can change this limit with -l/--limit. The limit must be a whole integer.

expand also includes the -I/--intermediates option, like extract. You should include this option if you plan to include it when you create your extracted module. For more details on this option, see extract.