Improve documentation repo organization

[antho1404]

Question related to to the doc:
Shouldn't we move the doc to a dedicated repo? Even better, having a dedicated repo that extract the docs from other repos?

Originally posted by @NicolasMahe in #112 (review)

[antho1404]

Concerning the repo for the doc, having it on a dedicated repo could be a thing, but I feel that will make it harder to maintain. The only issue with the doc right now is the starter kit doc. It cannot be merged within the starter kit otherwise, clients would have to maintain a doc that is unrelated to their application. Having a way to extract this information would definitely be a good thing. Maybe we could create a wiki in the starter kit app and synchronize this.