File service fix

* Fix a specific impossible condition which led to a specific bug when sending new data
  . There's a check for a previous fileid for a language, if it doesn't exist, get the one existing (with or without fileid), which leads to an impossibility to send another file for another language.
* Too much crutch and fallback in GET, if the fileid is not there, just send back a 404

PS: Might break some existing uploads. Resend the files, delete the resource just in case (but it should work anyway)