Add more usecases to the Demo Project

**What it's the actual situation on ARA ?**
The DemoProject contains basic features about ARA, but for presentation purpose of the products, the features in it aren't enough.

**Describe the solution you'd like**
Here is the features which can be useful in case of a presentation of ARA :

* [ ] Use 3 day cycles : `dev`, `stab` and `master`
* [ ] Use night cycles for `dev`, `stab` and `master` with several countries in them.
* [ ] Add a clean history (a "full green" history, then a red execution to show a proper regression) ideally on Stab
* [ ] Add a significative aggregation on the errors in the problem creation screen (like from 1 error to 100)
* [ ] Add videos & screenshots
* [ ] Reduce Gherkin's sizes (projector in presentation)

**Describe alternatives you've considered**
Add a persisted database locally, but it impose to keep the datas somewhere. If we put them in the DemoProject, we can generate them whenever we want.

**Additional context**
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