Allow current postgres config to run on GAE

[stefpiatek]

Preparing for today's demo I found two things that needed fixing:

• On the unsurprising side: had the same permissions issue for copying file into the postgres container, so had to update that in the Dockerfile
• Suprising side: orthanc's postgresql plugin was complaining about the database being corrupted. It was the commit where we added in the new schema and tables to the postgres startup. It looks like us setting pixl as the schema name for a database pixl is something that the orthanc plugin doesn't like 🤷. What I don't quite get is why this didn't come up in the system tests that are running in CI