DS-7847 : ds.open needs to include org.eclipse.zest.core and org.eclipse.zest.layouts

- Added Zest bundle to Open Sdk
Deb this "pre-3_8" look old, according to http://www.eclipse.org/gef/downloads/index.php the 3.8.2 = 2013/01/14, 3.8.1 = 2012/08/20, 3.8.0 = 2012/06/11 .. Is there any particular reason why you've opted against using the latest GEF (incl. Zest) 3.9.101 here?