Expose the simulation results through sim-lib

[bjohnson5]

Describe desired feature
Currently the payment results are logged to a csv file, it would be nice to be able to query simln during the simulation and get the current stats for the running simulation. This could be achieved by adding some public functions to sim-lib that return the current simulation results. This would allow a project that uses sim-lib to get payment statistics directly during the simulation, in addition to the results being written out to a csv file.

Use case for feature

Projects that depend on sim-lib could get runtime statistics to show the user while the simulation is running.

Would you like to contribute code for this feature?

Yes, I would like to submit a PR for this feature.