Started adding concrete instance of Vertex and Edge
Setup for building unit tests
Added OUnit hack (borrowed from Frenetic) to get tests running
Added single-node topology parser test
Dot printing includes vertices

- Network to_dot prints vertices as well as edges
- Vertex and Edge signatures include to_dot separate from to_string
- Node and Edge provide correct-ish to_dot implementations
Fixed dot printing of network edges
Added single-edge test
Changed ports to be int64
Added more parser unit tests

- Single bidirectional hop
- Two hops in a row
- Two bidirectional hops in a row
Moved Concrete module into oasis InternalModules

There's no need to expose Concrete directly as the concrete network
instantiation is already exposed as the Physical module in Network.
Fixed parsing of edge ports from Dot files
Add and expose Hashtable with vertices as keys
Renamed and moved things for better typing

- Concrete implementations are exposed via Network_Physical module
- Physical Network module is now Net in Network_Physical
- Changed names accordingly
- Changed _oasis
Added utility functions for Link type
More type hackery
Added find_edge function for the edge between two vertices
Added Bellman-Ford implementation
Added Floyd-Warshall algorithm for shortest paths
Correctly update node and edge counts when parsing DOT and GML files
Expose number of vertexes and edges