Make Ripcord-specific topologies optional
If ripcord.dctopo imports properly, then include its topologies in thelist of available ones. Also replace topo.py with new generictopologies and update paths.
Support more topologies
Move TreeNet to new Mininet API
Also remove all non-object-oriented legacy Mininet code and updatetests.
User-space compatibility is untested, but most of the code for it isstill in.