Support exporting a cluster type to DOT
Support exporting a cluster type to DOT

linus-sherrill/sprokit,mathstuf/sprokit,Kitware/sprokit,mathstuf/sprokit,Kitware/sprokit,mathstuf/sprokit,mathstuf/sprokit,linus-sherrill/sprokit,linus-sherrill/sprokit,linus-sherrill/sprokit,Kitware/sprokit,Kitware/sprokit