Add a "automatic translator writer"

[docteurklein]

It could write an empty trans key automatically if doesn't exists (at runtime).

eg:

1. call the translator with given key
2. if the key does not exist, write it in the trans files
3. display the string

EDIT: finally, i'm not sure it's usefull after introdcution of the "extract" command. (or just for messages not coming from templates)