Centralized knowledge base for Geppetto-Meta distribution

* Current documentation: https://github.com/openworm/org.geppetto.docs (http://docs.geppetto.org/en/latest/devdocs.html)
* Geppetto Meta website will be the new entry point
* Reuse Geppetto Showcase Markdown approach
* For development documentation we can also think about using github wiki or gitbook https://www.gitbook.com/
* Or other tools: Sphinx, etc...

Start by reviewing the current documentation at org.geppetto.docs and the Geppetto Meta website entry point. Compare the Geppetto Showcase Markdown approach with the listed GitHub Wiki, GitBook, and Sphinx options. The work is done when a centralized knowledge-base approach is selected and established as the new entry point.

Written by the indexing model from the issue text.