Doc: Update example used for QML getting started tutorial

Update the example project referred to in Getting Started with Qt
Quick tutorial.

    - Fix coding/comment style issues
    - Change plugin TARGET name, Use /imports as the
      destination directory
    - Fix qmldir with proper module info, delete unused
      qmldir from /core
    - Add a .qmlproject file

Change-Id: If269e61fb76399faae753469dc251d07cc219139
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>