Update base image and default to postgres 13. (#493)

Update base image and default to postgres 13. (#493)

FEATURE: update to PostgreSQL 13.

* postgres.template.yml: update to new major version of 13.

This changes the default postgres version to 13 for the postgres
template.

* images/base: bump postgres to version 13.
* postgres.13.template.yml: add postgres 13 template.
* postgres.12.template: add step to remove pg 13 install.
* launcher: increase timeout allowed for docker stop.

With large databases Postgres may take some time to stop gracefully, so
increase the allowed timeout.

* launcher: use temporary pg13 image while build is running.
Note this will be updated once the image change lands in master.