Export layer to CSV

[isaisabel]

As a user of ATT&CK Layers in Python, I want to be able to convert a layer into an easily readable/editable CSV file.

Each row should be a technique.
Each column should be a technique property/annotation, e.g color, score, comment.

Further considerations should be taken on how to encode the non-technique layer data (sorting, domain, name, description) in the CSV.