Rename production folder

[jravenel]

As of today, the production folder of naas is a symbolic link that is displayed to the user with : "⚡ → Production"

Following a few feedback from Pythonistas, this is not a good name as it is not connected to any convention.

The proposal is the following:

**rename to __production__

This way, naas become more compliant to the Python syntax in the same vein of :
__init__

The init.py files are required to make Python treat directories containing the file as packages. This prevents directories with a common name, such as string , unintentionally hiding valid modules that occur later on the module search path.

or __main__

__main__ is the name of the environment where top-level code is run. “Top-level code” is the first user-specified Python module that starts running. It's “top-level” because it imports all other modules that the program needs. Sometimes “top-level code” is called an entry point to the application.

A tentative definition would be:

__production__ is the name of the folder in Naas where the production-grade notebooks code run. “Production-grade notebook” is the user-specified Python code that starts running when scheduler, webhook, asset or dependency is present. It's “production-grade” because it leverages papermill in the background that parametrize notebooks for automated execution.

@Dr0p42 what do you think?