Add more robust logging

[alberdingk-thijm]

A possible extension to the tool that would be handy from a development and debugging standpoint would be more robust logging. We could add a new dependency (e.g. logs) and use it to allow users to write logging information to stderr or to a file.

[DKLoehr]

Can you be a little more specific? What sorts of logging do you think would be useful? If you just want to add the logs dependency, go ahead.

[alberdingk-thijm]

There are a couple of different forms logs could take. One option would be to print debug messages describing where we are in the control flow, e.g.:

[DEBUG] successfully parsed input
[DEBUG] running SMT with classical encoding
...

Another possibility would be to have logging describe what transformations are being run, what happens when certain functions are run, and so on. I don't consider this a high priority issue: more of something that might be nice to add for the off chance that someone wants to see what nv is doing without browsing the source code, or if someone is developing with nv and wants to inspect the control flow at a glance without needing to add a bunch of print statements (of course, if they want to do something more technical, they will need to dig into the code anyway).