Repository and Package renaming, part two: Mathics3-Frontend-xxx

[rocky]

Mathics3 now has several frontends, and I propose yet another renaming of GitHub repository and package names.

Just as we have Mathics3-Module-xxx, I suggest we start tagging front-ends as such with Mathics3-Frontend.

In particular, we have:

1. Mathics3-notebook-frontends -> Mathics3-Frontend-notebooks
2. Mathics3-notebook-jupyter -> Mathics3-Frontend-Jupyter
3. Mathics3-live -> Mathics3-Frontend-live
4. Mathics3-django -> Mathics3-Frontend-django
5. Mathics3-script -> Mathics3-Frontend-script

The first 3 are relatively new, so those should not cause much disruption. These could be done first.

The last 3 have more of a history, so these could come later.

Thoughts?

[aravindh-krishnamoorthy]

One of the things I've always liked about Mathics3 is the inuitive naming of the repositories. I think this is a welcome change (note: I only use Mathics3-Frontend-Jupyter).