Add row unpacked income_statement_ferc1 table

[zaneselvans]

We developed some tools for unpacking FERC Form 1 tables that are organized by row number (where each row should really be a column in a database table) for some client work, and this allows us to make a bunch of financial tables much cleaner and easier to use.

To make this happen we need to:

• [x] Compile a row map for the f1_income_stmnt table
• [ ] Compile a row map for the f1_incm_stmt_2 table (2nd half of the form... in another table?!)
• [ ] Write a new pudl.extract.ferc1.income_statement() function.
• [ ] Write a new pudl.transform.ferc1.income_statement() function.
• [ ] Compile a tabular data resource specification for the new income_statement_ferc1 table.
• [ ] Debug or document any data issues that come up during the ETL process.

[zaneselvans]

All of these tables were addressed in the XBRL FERC 1 refactor. See #1574