Update README: how to obtain `ipcc` database
Extract target database selection from SQL scripts to shell scripts

The target database used to be specified in each and every
SQL script, with `USE 'giec'` instructions.

I have removed these instructions, and provided the name of
the database as parameter to `mysql` client instead. This
name is configured in a variable in each shell script.
Switch source database from `giec` to `ipcc`