Re-land r29957 (add versions and constraints for packages and samples), with

tools/publish_all_pkgs.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 #
 # Upload all packages in pkg/ (other than a few that should be explicitly
 # excluded), plus sdk/lib/_internal/compiler .
 #
 # Usage: publish_all_pkgs.py
 #
 # "pub" must be in PATH.
 
 
 import os
 import os.path
 import subprocess
 import sys
 
 BLACK_LISTED_DIRECTORIES = ['.svn', 'async_helper', 'expect', 'third_party'];
 
 def Main(argv):
+  pkgs_to_publish = []
+
   for pkgdir in ['pkg', 'pkg/third_party']:
     for name in os.listdir(pkgdir):
       if os.path.isdir(os.path.join(pkgdir, name)):
         if name not in BLACK_LISTED_DIRECTORIES:
           pkgs_to_publish.append(os.path.join(pkgdir, name))
 
   for pkg in pkgs_to_publish:
     print "\n\nPublishing %s:\n-------------------------------" % pkg
     subprocess.call(['python', 'tools/publish_pkg.py', pkg])
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))