Finish initial feature set for bot management.

New stuff:
- Add command line args to main SteamBot.exe (using NDesk.Options)
- Bot manager spawns child procs each of which runs it's given bot.
- Add user interaction to bot manager command line interface. Users can
start and stop bots, and show config.
Modified stuff:
- Separate callback thread from Bot ctor (use Bot.StartBot) for
cleanliness.
- Configuration objects got ToString
- Log threw exceptions in finalization. Use IDisposable to play nice.