Add logic to ingest particular years from FERC1 DB
Add logic to ingest particular years from FERC1 DB

Previously, PUDL would automatically ingest all available years from the
FERC1 DB, meaning that if you only wanted some years pulled into PUDL, the
whole FERC1 DB had to be re-initialized.  This takes an annoying amount of
time, so I added logic to enable selection of only certain years of data
from a full FERC1 DB.

Resolves: #73

catalyst-cooperative/pudl,catalyst-cooperative/pudl