Check and update model list in index.rst automatically
# What does this PR do?

We currently have two lists of the models to maintain (in the main README and in the `index.rst` for the docs) which is painful. This script checks the mode list in the index.rst is a proper converted copy of the model list in the README and can also fix it with the command `make fix-copies` (same API as for the copies of parts of the model). It also enforces our maximum character per line so that the `index.rst` is still readable in an editor.


I'll let you rebase!