Implement language switcher

Change language without refreshing page
New file: definitions.json

To add notes for a language add this line to site in sites.json
> "notes_it": "Logga il tuo account, vai su parameters, clicca Delete my
account. Conferma cliccando I want to delete my account. E ancora
cliccando Delete my 9GAG account."

If site note not exists in the language the user choose it shows EN note
It also saves a cookie containing the language choosed for future site
visits