fix: /Makefile: postgres_restart-Linux: added pause after telling the user the command to run

/Makefile: $(postgresReload-*): use postgres_restart for the postgres-restarting step

bugfix: /Makefile: postgres_restart: added separate Linux version that deals with Linux-specific issues (as in $(postgresReload-Linux))

/Makefile: added postgres_restart, since this is often invoked separately from the entire postgres_reload target

/README.TXT: Full database import: disk space: increased minimum requirement to 500GB (~200GB extra), as the import may use significant additional space for temp tables

/README.TXT: Full database import: documented that env vars set before invoking `screen` will be inherited by it, so these steps will work even if they come before `screen`

backups/TNRS.backup.md5: updated

/README.TXT: Full database import: added steps to set a custom version, if the auto-assigned one would cause a collision with the last import

/README.TXT: Full database import: `unset version`: documented that this is needed because it may have been set in the outer shell

fix: lib/sql_io.py: put_table(): don't warn if can't create pkey, because this just indicates that a set-returning function was used. this should get rid of the last of the confusing benign warnings in the test output.