Removed Digraph
Broken test
Merge branch 'master' of https://github.com/frenetic-lang/frenetic
Import Merlin's Topology module

Added ocamlgraph as a dependency
Updated topology use in Controller and ConsistentUpdates
Expanded topology interface

Included shortest path and edges ports functions
Functions through appropriate exceptions
Removed NetCore_Topo and NetCore_Graph
Merge new topology fork with frenetic-lang:master
Re-added NetCore_Graph to get NetCore_Verify to compile

NetCore_Verify should be rewritten against NetCore_Topology and ocamlgraph.
I don't have time to fix it right now so I'm leaving it in for the time being.
Forgot to check in oasis-related changes for re-adding Digraph
Merge branch 'master' of github.com:/frenetic-lang/frenetic