Consider adding a section to the README on DOCKER_USER and/or data directory permissions

[toolness]

When going through the README instructions, we ran into some file permission errors because containers couldn't write to the data directory. This is likely because our uid on our system was 1000, while the one specified in the .env file as DOCKER_USER was 1100. We actually just ended up making the data and data/elasticsearch directories world-writable, but a more secure fix would probably involve adding a section to the README advising the user to set DOCKER_USER to a value appropriate for their system. Since that would involve editing the version-controlled .env file, however, it might make sense to rename .env to .env.sample and have the user explicitly create their own .env file.

[SPTKL]

I agree! I think the default 1100 is mostly set up to work with the setupServer.sh script

labs-geosearch-docker/setupServer.sh

Line 9 in 5b2d889

sudo useradd --create-home -p $( echo pelias | openssl passwd -1 -stdin ) -u 1100 pelias

We can probably change the setupServer.sh so that it would take the uid from the .env file