Android/feature/activity stream

[fihlie]

As stated in #378 👍 Activity stream is a model for representing potential and completed activities using the JSON format and a core functionality for this project. Activity stream coming from backend should be displayed on mobile.

The meeting notes:

https://github.com/bounswe/2021SpringGroup11/wiki/Meeting-20.2---24.12.2021

Related backend issues:

348

347

346

344

342

326

Thanks to all my friends in backend, they have successfully implemented W3 Activity Stream. And in this PR following features are implemented:

• Activity Stream Connection with backend
• Activity Listing on Mobile (you can navigate through bell icon)
• Refresh Button for Activity List
• Some UI improvements to increase responsiveness.

[fihlie]

Updates have been made based on feedback