Pre-download tapplet logo

[kowalski]

All the images should be fetched and stored locally in the process of syncing with registry.

When displaying them in Tari Universe UI we should be pointing to image files served on localhost rather than the original URLs. This way:

• we won't leak privacy information about people using app in the runtime
• more importantly, if the original url goes down our UI will not show it as broken, but serve from cache