[SERVER] Challenge configuration

[andreaswachs]

What needs to be done?

There needs to be general configuration for each challenge, such that the server knows of its existence.

The challenge configuration serves as a store for challenges, in order to reduce configuration duplication.

Challenges needs to have some data points configured:

• Challenge name
• Challenge ID
• Docker image
• Memory usage

Challenges will be referred to by their challenge IDs.

Acceptance criteria

• Challenge configuration is reflected in Go structs
• Can Unmarshal challenge configuration to Go structs