DB schema bootstrap script now runs silently by default

When you run `bin/create_oq_schema` or `bin/oq_create_db`, you don't get flooded with CREATE and INSERT statements. Now, you just get a message summarizing each phase of the script.

You can enable verbose output by using `--verbose` or `-v`.

Also, `create_oq_schema` is now a symlink to `oq_create_db`. Before, they were both copies of the same thing.