Native Launcher: Better approach to launching files from Desktop

* Add lines to Archi.ini for Mac and Lnx:
  --launcher.defaultAction
  openFile
* Use a better approach as per:
* http://help.eclipse.org/kepler/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Fguide%2Fproduct_open_file.htm
* Now no need for specific Mac launcher
* Might work for Linux too if files are associated
* Use SWT.OpenDocument event