Migrate old Glottolog DB dumps to newer PostgreSQL

[chrzyki]

The old database dumps listed here:

https://github.com/clld/glottolog3/blob/f3a431622446603b31f63316550e82be9bf95221/glottolog3/releases.ini

Should be 'migrated' to a newer PostgreSQL version, most likely PostgreSQL 10. This entails:

• downloading the dumps
• loading them into a database running the preferred PSQL version
• dumping them again from there
• uploading them again to cdstar
• changing the bitstream identification in the aforementioned releases.ini to the bitstream of the newer, migrated version

[xrotwang]

If we have a script to do this, we might even add dumps per pg version as bitstreams to the CDSTAR objects. This would future- and "past"-proof our setup.