GNS3 Docker support

by gcetusic for Python Software Foundation

GNS3 is a network simulator that uses Dynamips, VirtualBox and QEMU to simulate network nodes. Docker is a highly flexible VM platform that uses Linux namespaces and cgroups to isolate processes inside what are effectively virtual machines. This would enable GNS3 users to create their custom virtual machines and move beyond the limitations of nodes that are network oriented and because of its lightweight implementation, would make it possible to run thousands of standalone Linux servers on GNS3.