Do not catch specific exception if not doing anything specific with it.
Catch all and transform to Json to forward back to response with HTTP
error code.
Implemented getNewElfin with new ELFIN.Id generation. 
Reviewed exception / application validation management.
Improved and finalised getNewElfin, createElfin and updateElfin Api
functions implementation.
First draft elfinDelete implementation. Only deletes the ELFIN but not
the MELFIN element enclosing it nor the actual "file" in the database.
Will be corrected.