Refactor: Create config struct for simulator

[carlaKC]

1. Add a SimulationConfig struct that passes all the configuration options to the simulator rather than individual params.
2. Make log_interval configurable while we're here (currently hard set to 60s)

Started working on this in e929a2d in #141 but decided to leave for a follow up.

[enigbe]

@carlaKC I started working on this while waiting for a review. Curious about what should rank higher between CLI arguments and values in a conf file.

I think it would be preferable to have CLI arguments override the conf file if they're passed but happy to code it any other way you'd prefer.

[carlaKC]

I think it would be preferable to have CLI arguments override the conf file if they're passed but happy to code it any other way you'd prefer.

I think this makes sense, perhaps with a log warning that a config file value has been overwritten?