Fixes for the Hello World notebook

[SagiPolaczek]

Visit here to watch the updated notebook

So following #278 , I encountered this annoying problem which makes us to restart the google colab notebook's runtime after the first Fuse's installation. Unfortunately I couldn't find a really good solution for that. The best workaround I came up with is to add a clear explanation for the FuseMedML installation 😵 . (OPEN FOR SUGGESTIONS)

Changes:

1. Fixed prefix for model's outputs
2. Added a clear explanation for the FuseMedML installation on the google colab notebook.
3. Improved UI
4. Re-open the notebook's unit-test

Thanks @simona-rc for raising those issues 😄

Update: double checked on Jenkins:

Update 2: Fix typos in the installation instructions: [all+examples] -> [all,examples]