Create database loading script for SQLite

Update the load_psql.sql script to use SQLite.

Unlike load_psql.sql, make the ``$DATABASE`` variable a parameter.

Use a variable for the CSV filename to make commands more DRY.

I only tested this for the P12 table for Illinois tracts, i.e.:

```
./load_sqlite.sh P12 17 140 nicar.db
```