Improve setup guide

[ykorzikowski]

During setup, I found:

Problems

• docker-env variables are not used in config

• odoo user has no fixed UID (bad)

• initial setup needs:

  • docker exec -it odoo-web-1 id
  • chown -R <id>:<id> /mnt/odoo
  • docker exec -it odoo-web-1 odoo -i base

Improvements

• use sed/echo to create odoo-config from env vars

• add user odoo with fixed UID (and add it to documentation)

• check first run (maybe with a lockfile) and run the odoo -i base on first run

[lathama]

These are all good points. After I can get the issue count below 100 this is a great issue to start on.