Cookbook FAQ updates & Contributors section

Summary

Various documentation improvements:

• Remove obsolete paragraphs from the FAQ
• Move the contributors list to the CookBook
• Add recent contributors: Cédric Traizet (CS) and Gaëlle Usseglio (THALES SERVICES)
• Remove out of date Monteverdi README
• Update google groups links to the new forum

Rationale

Part of the story to move all docs to the cookbook. See #1679.

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

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Check before merging:

• All discussions are resolved
• At least 2 👍 votes from core developers, no 👎 vote.
• The feature branch is (reasonably) up-to-date with the base branch
• Dashboard is green
• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement