Make app detail page resilient against missing Screenshots.

Screenshots can be nil in Services returned from CSA. Make sure javascript
can handle this.
Display proper message depending value of Attribute Release Policy.

There are 3 states:

  1. No release policy
  2. A release policy that will share no attributes
  3. A release policy that will share certain attributes

Depending on the state a proper message or the attributes that will
be shared will be shown.