Attempt at revised/simplified topo class:
- keys are strings- metadata is simply a dict- buildFromTopo greatly simplified
Re-added TreeNet convenience function.
Restored numbering of tree nodes.
Moved TreeNet() convenience function here.
Changed TreeTopo() to number hosts from h1 to hN.
Added two spaces before in-line # comments.
Removed underscores for public Node methods. Minor cleanup & comments.
Added mininet.topolib to store useful topologies.