Add changes from the SEP project - Robust Waterproof

[TheTechZone]

This includes the work done to :

• parse the AST returned by SerAPI for sentences written in the editor.
• port the tactics library to Ltac2
• create an updater for waterproof and an installer for Waterproof's dependencies.

Ideally, I propose merging the changes in a separate branch and not develop directly, to prevent any compatibility issues.

Some of the files were created for the SEP project's scope. A few subsequent changes might follow (e.g. removing some of the v files) to remove parts not relevant to further Waterproof development.