Optimize database dumping and loading procedures

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Database dumping and loading procedures are interdependent.

In the current framework:

• Database is dumped into .sql.gz, which takes about 1 hour to dump and compress a 90GB .sql file. The .sql.gz format is selected to make database dump files completely reproducible, which is one of the key requirements for PedOT project. The custom format, dumped with -Fc option, can speed up database loading, which is suggested by Shiping Zhang, but the custom format dump files have different sha256 checksums for different dumps for the same database.
• Database is loaded using psql, which is the only compatible tool for loading .sql.gz file. The loading process takes about 1.5 hour to decompress the .sql.gz file and load the 90GB .sql file. After loading, one index is created, which takes about two hours.

cc @blackdenc