AWM should not change the translation page scope

To reproduce:

• create an application
• change the translation page scope (to WIKI for example)
• edit the application to add a new field

--> the translation page scope changed to ON_DEMAND

When creating a new application a related translations document is created with on demand scope which is great.

Now if for any reason the application author change it (I'm not asking for any new UI here) it should not be broken when using AWM UI to add a new field.

In general once the translation document is created AWM should only modify the actual translations keys IMO.