Log data during network simulation/evaluation, produce plots and animations

[czlee]

• If given a datafile= argument, rat-runner will log a bunch of information about the network and Remy (signals, actions, throughput, delay, window size) as it is running, and produce a protobuf with this information.
• Protobufs compilation now also produces Python files.
• Added new plot_log.py script that generates a bunch of plots and animations. Not all of them are insightful right now, there are just lots of them to provide a framework for finding the most useful views.
• ConfigRange now also takes simulation_ticks and log_interval_ticks which control the maximum simulation running time, and how often logs are taken, respectively. If log_interval_ticks is zero then it'll just log everything. These have default values in the protobufs, so existing config files should be backwards compatible.

[keithw]

Changing the scripts is no problem, but I'm uncomfortable threading so much logging-related code through all of the code that doesn't really need it (the optimizer, the sender-runner, etc.). Can you write a separate sender-logger program that does its own thing off to the side (probably skipping SenderGang, and maybe skipping Network too)?

Also, as you know I think logging to huge protobufs is a bad idea! The protobuf library does not do well with gigantic protobufs. A text file delimited by newlines is probably easier (since you can parse it line-by-line).