Remove FileException, DirectoryException and LinkException from dart:io and use FileSystemException instaed. BUG=https://code.google.com/p/dart/issues/detail?id=12461 R=nweiz@google.com, sgjesse@google.com Review URL: https://codereview.chromium.org//26968003 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/watcher@29168 260f80e4-7a28-3924-810f-c04153c831b5