Simplification of Variables design

[sylvlecl]

Description

The variables module has a very complex design, including chained lists of templates.

The contract for variables is not explicit, making it error prone.

Instead, we should use a more classic design where:

• variables all implement the same interface
• list of variables are plain classes, not chained templates

Implementation note I am aware that this brings some computation from compilation time to runtime, but it will clearly make NO difference overall in a computation ...