Improve OAuth2 integration

helper/crypto.go

locale/translations.go

locale/translations/fr_FR.json

server/oauth2/google.go

server/oauth2/provider.go

server/routes.go

server/static/bin.go

server/static/css.go

server/static/js.go

server/template/common.go

server/template/html/settings.html

server/template/template.go

server/template/views.go

server/ui/controller/oauth2.go

sql/sql.go

storage/user.go