* Adding a help button on top of the chat, that links to the online documentation on frama.io.
* Replaced github.io documentation links by frama.io documentation.
* Adding links to the documentation in the diagnostic tool.
To make the Weblate integration simplier, this commit merge all
translations in yml files (there is no more distinction between
standards and settings strings)
This yml files will be handled by Weblate.
TODO: document the new translation process.
