working through translator/Extensions with some reorganization and generalizations

doc/translation.txt

@@ -28,6 +28,7 @@ This will take a long time (ten minutes or more) and will probably require at le
 ```
 with obviously the possibility to vary the source and the target language.
 
+
 4. To modify the sources, work on the files in
 ```
   GF/lib/src/translator/