console: configurable log levels, file logging (#359)

[iceiix]

No description provided.

[iceiix]

Current status: this works, logging to client.log in the configuration directory (as of #486, this is either the current working directory -or-:

// Lin: Some(/home/alice/.config)
// Win: Some(C:\Users\Alice\AppData\Roaming)
// Mac: Some(/Users/Alice/Library/Application Support)

), and to the terminal (now with color). But now nothing logs to the in-game console, nor the browser console (for #446 web). And configurable log levels would be nice, instead of hardcoding trace (add options in conf.cfg?). In particular, the terminal log output could have a lower log level to reduce console overhead, but keep the file log level higher (trace? debug?) for diagnosing problems after they happen.

Also allow disabling terminal colors, if it causes problems (TermLogger -> SimpleLogger, depending on a config option).

Maybe stop logging to the in-game console, and use it instead for #479 chat, and other client/server messages. It has a different purpose than diagnostic logging (trace/debug/info/warn/error).

[iceiix]

It was more straightforward to extend our existing logger backend than switch out to another logging system.

Added file logging and configurable log levels (edit in conf.cfg). The default of info for terminal (and trace for file) should help cut down on the stdout output, especially while network debugging, but keep this valuable information available in the log file (client.log).

Removing logging to the in-game console can come later, after #479 chat. Adding colors to the terminal output would be nice too, just like there are in the in-game console, using TextComponents (but not strictly necessary. convert the TextComponents to ANSI codes?):

        let mut msg = TextComponent::new("");
        msg.modifier.extra = Some(vec![
            Component::Text(TextComponent::new("[")),
            {
                let mut msg = TextComponent::new(file);
                msg.modifier.color = Some(Color::Green);
                Component::Text(msg)
            },
            Component::Text(TextComponent::new(":")),
            {
                let mut msg = TextComponent::new(&format!("{}", record.line().unwrap_or(0)));
                msg.modifier.color = Some(Color::Aqua);
                Component::Text(msg)
            },
            Component::Text(TextComponent::new("]")),
            Component::Text(TextComponent::new("[")),
            {
                let mut msg = TextComponent::new(&format!("{}", record.level()));
                msg.modifier.color = Some(match record.level() {
                    log::Level::Debug => Color::Green,
                    log::Level::Error => Color::Red,
                    log::Level::Warn => Color::Yellow,
                    log::Level::Info => Color::Aqua,
                    log::Level::Trace => Color::Blue,
                });
                Component::Text(msg)
            },
            Component::Text(TextComponent::new("] ")),
            Component::Text(TextComponent::new(&format!("{}", record.args()))),
        ]);