Docker improvements

[julichan]

Thanks for the quick docker security fix previously. I'm planning to add several features later such as

• multiple dashboards
• multiple users

I think we should discuss this so we can help each others but that's not the conscern of this PR.

Here are few docker improvements you might want which i needed for proper security/usage on my side:

1. use a folder for the database, this allow the usage of named volumes wheares file mounting is feature limited.
2. removal of the expose component in dockerfile. For a reason, see Expose vs publish => expose is for development purposes and should not end in a production image. Publish adds a security layer whereas Expose does not not. Moreover Expose component result in the display of non opened port in docker ps command and the internal container port is configurable where Expose component is not configurable nor removable from another dockerfile.