Improvement: Use an even amount of spaces for indentation

### What

Using an uneven amount of indentation (three spaces at the moment) makes the github review "suggestion" feature very uncomfortable because there a tab indents by two spaces. Also most IDEs can deal better with an even amount of indentation. The most common for python code and also other things is four spaces.

### How

Change all S-CORE style guides and documentation to use either two or four spaces for indentation.

### Estimates for realization

Large effort now. Huge effort if we ever need to do that later.

### Category

- [ ] Affects Detailed Design

### Requirements / Architecture

- [x] Requirements / Architecture are not affected by this change?