* Corrections dans concept-aliases.md version fr
* Some correction in intro-upgrade-from.md French version
* some corrections in start-databases.md French version
* added translation of structure-applications.md French version
* adding source change in translation of concept-alias.md
* adding source change in translation of intro-upgrade-from-v1.md
* added French structure-extensions.md [skipci]
* some typos [skip ci]
