Add a general overview for the gamma-ray data analysis

[registerrier]

The gammapy documentation starts with an overview page. See code here: https://github.com/gammapy/gammapy/blob/master/docs/overview.rst

It should be written with a section on:

• Gammapy concept
• Gammapy workflow
• DL3 data format
• Data reduction
• Modeling and Fitting

The text should be kept short with many links to general API documentation and notebooks .

Some figures must be prepared:

• gammapy in the scientific python context
• gammapy workflow

[cdeil]

I'll spend a few hours and write a first draft of docs/overview.rst now.

I'll start with just some text and bullet points, linking to many other pages and tutorials and the API docs of the most important classes. Figures can come later.

@registerrier @adonath - For overview.ipynb, what's the plan? (see here what we have now)

I can leave that for a second PR, after docs/overview.rst is done, but it would help if there is a plan what docs/overview.ipynb would contain. Is the idea that we have zero code snippets in docs/overview.rst, and then in docs/overview.ipynb we import all the major classes and show how to create one of those objects (i.e. EventList, DataStore, datasets, models, ...)?

[cdeil]

First draft written in #2622 . OK for v0.15 (see https://github.com/gammapy/gammapy/pull/2622#issuecomment-560403958), should be improved for v1.0. Keeping this issue open.

[registerrier]

A daughter page has been added in PR #2721 that explains DL3 data. Some figures have been produced and stored in gammapy-extra:

-https://github.com/gammapy/gammapy-extra/blob/master/figures/general/data_flow_full.png -https://github.com/gammapy/gammapy-extra/blob/master/figures/general/data_flow_gammapy.png

[Bultako]

We have now a specific page Package structure in the docs which addresses this issue.

There's though still most of the content to add to the Gamma-ray data analysis, so I reword a bit the label of this issue and keep it open.

[Astro-Kirsty]

@registerrier, I think this can be closed now?

If not, I will add it to the new documentation issue I am creating!

[registerrier]

Yes this can be closed.