More clear definition of APPDATA_PREFIX override value

[kshychko]

Expected Behaviour

Sometimes solution requires for deployment units to share the same APPDATA_PREFIX. In this case we can override it using DefaultFilePrefix setting

Current Behaviour

In order to do that DefaultFilePrefix settings needs to be defined in the component settings.json file.
But this file is also used to define a component settings for the purpose of setting env variables.

Possible Solution

We need to think of more clear way to define and use this settings as Hamlet engine feature and don't mix it with a component environment configuration.

Context

APPDATA_PREFIX was changed, when DefaultFilePrefix was removed from settings.json file and added to a deployment profile as a setting. It was ignored due to this change, which let to the problems for application to retrieve the existing files from S3 because of the incorrect prefix.