[Translation] added LoggableTranslator.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #3015, #2435
| License       | MIT
@fabpot the default would still be kernel.debug, but exposing a dedicated configuration setting would allow the config to be a bit more flexible (you might want to enable such logging in your preprod environment even if it does not run in debug mode)