Move entity class into Entity-directory

[modir]

In the getting started tutorial is a section about the model files. It is stating that they are often called entities. In the most projects I have seen in the last few years people moved the entities into a Entity-directory. I think this is a a good thing and should be already done like this from the beginning. Hence I would propose to change the documentation accordingly.

What do you think about it? I could create a pull request if this would be of interested.

[settermjd]

Hi @modir, if that's been your experience and you're keen to create a PR, please do so. Thanks, in advance, for taking the time.