Simplify Docker setup

[alsciende]

Hello folks. I wanted to set up a local nrdb and found your cool Docker files. A few things in the docker-compose.yaml file surprised me and I tried to understand it. I think I found a simpler setup, let me know what you think. It works for me.

• removed the named volumes on /vendor and /var which are in .gitignore anyway
• removed the named volumes on /bin and /web because there's no reason they would be changed unexpectedly. The data in /web is already ignored by .gitignore.
• removed the named volumes on /app/config because I created a mount volume on /app/config/parameters.yml instead of copying files around

Consequently, I simplified docker/docker-first-run.sh too because no files need to be copied.

Benefits of this MR:

• Faster setup
• Easier to understand and maintain
• The vendors installed by "composer install" in vendor/ are accessible outside the container, so available to the IDE
• The logs files in var/log/ are accessible outside the container, should you need them

[plural]

looks great, thanks! We set up the initial docker stuff a long time ago and the two of us that did it were fairly new to docker so it was ... messy!