Configuration file for bot and plugins

[brenns10]

Currently we provide all bot configuration on the command line. I've begun creating launcher scripts which contain all the options, so functionally we're abusing bash scripts as configuration files.

This actually isn't awful; it has worked for a while. But we've reached the point where plugins should be able to have configuration of their own, and this can't be achieved with command line arguments.

Integrate with libconfig (or an INI parser) to allow cbot to accept a configuration file.

[brenns10]

Implemented in 975978b