Release Talkyard v1

Currently preparing Talkyard v1 — a new epoch.

Talkyard v1 will upgrade 3rd party software, e.g. Postgres and ElasticSearch.

To upgrade from v0, you'll install Talkyard v1 in /opt/talkyard-v1,
then take a backup of your existing Talkyard installation, located at: /opt/talkyard,
then restore the backup into /opt/talkyard-v1, while editing some config files a bit.