Update of AppsPlus API for MoreApps module

[pylapp]

Needs

The AppsPlus proprietary backend used by MoreApps module can send more types of data, mainly a carousel of applications. The module must be updated to deal with this new specifications.

Definition of Ready

• [ ] Get JSON files matching any cases (carousel, no carousel)
• [ ] Get a swagger or an API description explaining error cases and which JSON fields are optional

Definition of Done

• [ ] Update CHANGELOG
• [ ] Update README
• [ ] Update documentation
• [ ] Update unit tests
• [ ] For demo app, add a field to test some API key
• [ ] In DTO layer, deal with carousel
• [ ] In BO layer, deal with carousel
• [ ] Update GUI to deal with carousel