Restructure app [18h]

[amitaibu]

@rgrempel has explored some nice structure that provides a clearer separation between data and UI state, as well as a single source of truth for the data:

• The Backend as the name indicates is responsible for the data.
• Fetch is our way of managing which data should be fetched from the backend.

[amitaibu]

I've made the scope bigger, and increased the estimation. Since your code in private project is quite general and already documented it will be a lot of copy/ paste - so I think the estimation might be enough.

I'd love to see this done sooner than later, so we could start copying to other projects.

[rgrempel]

I'll get going on this once the private project settles down a bit ... . It will make a nice companion for some blog posts, as I'll have some public code to refer to!