Start import script: update submodule and retrieve short hash
Rename database to ipcc_facts_import

Use singular for 'import', like in project name.
Rename database simply to `ipcc_facts` (remove `_import`)
Create SQL script import.sql in import.sh

At this step, the script only creates an empty database `ipcc_facts`.

I also added a rule to .gitignore to prevent adding import.sql to the
git repository.
Add Usage section