Improve configuration and deployment #21

Configuration

More aspects of the application should be configurable. And configuration should be possible in different
ways; including but not limited to: JSON files, environment, maybe java properties.

Following things need to be configurable:

• Type of code evaluation used (sandboxed/direct/forked)
• Sandboxing settings
• Default imports

It is important, that the application only runs if the expected type of evaluation is available.
Code should not run embedded in the server without sandboxing just because zookeeper can not be found,
the server should crash.

Deployment

Different types of deployments
need to be supported so that the code does not throw exceptions.

• Server with Document Store (supports sharing)
• Server without Document Store (does not support sharing)
• Code Evaluation in Server (embedded)
• Code Evaluation in Runtime (discovered using Zookeeper)

We should also create all kubernetes resources or even a helm chart

Thinking about the future

There are going to be different ways of deployment JSheets.
Individual components can be substituted and mixed together to provide a working application.
It should be simple and straightforward to specify all those components for both production and test environments.