Import edges from csv

# Import edges from csv

Many tools use csv as output format. Some of them, e.g. [code-maat](https://github.com/adamtornhill/code-maat) include dependency-information in them. Also the cc.json format for edges is quite cumbersome. It would be super cool if the CSVImporter could also read this information out of the csv.

## Description

As a developer, I want to specify edges in csv so that I can import them easily.

## Acceptance criteria

- Given a csv with header "path, to_path" i want to create a cc.json with all path and to_path nodes and edges corresponding to the csv.

Start by locating CSVImporter and reading how it currently handles CSV input and produces cc.json. Trace the representation of paths and edges, then verify behavior against a CSV with the header "path, to_path". Done means every path and to_path becomes a node and each row creates the corresponding edge.

Written by the indexing model from the issue text.