Enable Fiddler to load NetLog files via command line directive

CustomRules.js

	static function OnBoot() {
		var s = Environment.GetCommandLineArgs();
		for (var i=1; i<s.Length; i++){
			if (s[i].StartsWith("-netlog:")){
			//	FiddlerObject.log("Command line told us to import Netlog " + s[i].Substring(8));
				var oImportOptions = FiddlerObject.createDictionary();
				oImportOptions.Add("Filename", s[i].Substring(8));
				FiddlerApplication.DoImport("NetLog JSON", true, oImportOptions, null);
			}
		}
	}

https://twitter.com/ericlaw/status/1442927713874956292

lol. So, it turns out the reason that this is so poorly documented is that there's no reason to do this anymore.
ProfferFormat takes an optional third parameter specifying which file extensions an importer handles.
I've updated the importer.