Eliminate copy of graph objects to improve memory utilization

[msschwartz21]

There are at least two places where we create copies of the TrackingGraph:

• At the initialization of the Matcher
• When correcting shifted divisions

We should eliminate both of these instances. The first is easy, but the second may require more thought since we are essentially putting duplicate labels on the graph.

[msschwartz21]

#74 eliminated the copy of the graph that was created by the matcher, but copies are still created during correcting division frame shift errors.