[Cordova-JS] Platform-specific plugin directory structure

[Filip Maj]

How come we use the following dir structure for platforms:

lib
 - android
  - plugin
   - android
    - etc. etc.
 - blackberry
  - plugin
   - blackberry
    - etc. etc.

What's with the doubling-up on platform dirs? Do we need that? Seems
redundant (and not intuitive for folks adding new platforms, I.e. Bada)