New logging system

This PR revamps the logging system, re-writing it entirely. The code has pretty extensive documentation (I hope) but here are the highlights:
 - Multi-threaded logging, avoiding excessive logging from slowing down the emulation as much. (Especially on Windows where console writes are slow.)
 - Nicely trimmed paths relative to the source directory, without the source repository prefix.
 - Completely re-organized severity levels and log classes, with documentation providing guidelines for use of each class which should prevent misuse.
 - All the logging statements in the code have been updated to follow the new guidelines.
 - Runtime-configurable filter (currently read from the configuration file) allowing configuration of the log levels for each different log class.
 - Possibility of future extensions to support logging to the GUI or silencing of spammy log messages. (Planned for future PRs.)
Not necessarily, if I'm looking for parameter documentation specifically (and know the purpose of an obvious function), I'll look at the table. But meh, it's not something I care enough about to argue over, especially because you do a pretty good job of documenting anyway (as you said)