Feature/relational db

[ostcar]

PR for the relational db feature.

To test it, use the following steps:

1. Start Postgres
   docker run -it --rm --network host -e POSTGRES_USER=openslides -e POSTGRES_PASSWORD=openslides -e DATABASE_NAME=openslides postgres

2. Add the schema
   You have to be in openslides-meta/dev/scripts
   DATABASE_HOST=localhost DATABASE_PORT=5432 DATABASE_USER=openslides DATABASE_NAME=openslides sh apply_db_schema.sh

3. Build and start the autoupdate-service

go build
OPENSLIDES_PUBLIC_ACCESS_ONLY=1 OPENSLIDES_DEVELOPMENT=1 AUTH_FAKE=1 ./openslides-autoupdate-service

OPENSLIDES_PUBLIC_ACCESS_ONLY deactivates the connection to the vote-service
OPENSLIDES_DEVELOPMENT uses the default secred keys
AUTH_FAKE deactivates the connection to the vote serive (with the redis logout messagebus) and uses user id 1 for all connections

4. Connect to database
   psql -h localhost -p 5432 -U openslides -d openslides

5. Create User in database
   INSERT INTO "user" (id, username) values (1,'hugo');

5a. Make User a superadmin
UPDATE "user" SET organization_management_level='superadmin' WHERE id=1;

6. Connect to Autoupdate
   curl localhost:9012/system/autoupdate?k=user/1/username

Currently, this is an early stage. Lots of stuff will probably not work