Add data formatting abstraction layer

### Feature Description

The PX Engine will need a standardized/normalized way of providing unit-based and/or unit-less values in such a way that an outside interface can make sense of it.

We can start with adapting the way Lighthouse uses scores, values and units and see whether that covers all of our expected use cases.

Ideally, we would want a way to provide such values as a Value Object that comes with all the needed logic to allow for both numerical analysis/comparison as well as string-based representation. We'll need to consider localization as well.

Start by reviewing the feature description and how Lighthouse represents scores, values, and units. Clarify the expected unit-based and unit-less cases, numerical comparison behavior, string representation, and localization requirements before implementation; done should be an agreed abstraction that covers the expected use cases.

Written by the indexing model from the issue text.