Create reduced-order simplified network

The TAMU network contains topological data that is unnecessary for the purposes of our simulations. The clearest example of this situation is 'stubs': nodes which are only connected to a single branch. These nodes can contain demand ('load stubs'), generation ('gen stubs'), or nothing at all ('null stubs'). The branches of gen stubs should never constrain the power flow from the generators, and likewise the branches of load stubs should never constrain the power flow to demand. Under these conditions, a multi-period DCOPF would produce an identical dispatch if the loads and/or generators were moved 'upstream' one hop closer to the main network and these redundant branches deleted, while the size of the required model would be reduced.

In the full USA network, the 82,000 nodes can be broken down into:
- 55,658 nodes (68%) with more than one connected branch
- 13,790 nodes (17%) of load stubs
- 6,445 nodes (8%) of gen stubs (only one generator)
- 1,802 nodes (2%) of gen stubs (multiple generators)
- 4,305 nodes (5%) of null stubs

This suggests that we can eliminate approx. 25% of the buses and approx. 20% of the branches with no loss of accuracy.