Handle errors during master startup

Print a message urging unhandled exceptions thrown by startup to be
reported to the GitHub issue tracker and initiate shutdown.

CHANGELOG.md

@@ -3,6 +3,7 @@ Version 2.0.0
 
 - Fixed sslCert and sslPrivKey entries being ignored in the config.
 - Changed ssl key creation to be done at startup instead of on npm install.
+- Added error handling during master startup.
 
 Breaking Changes
 ----------------

master.js

@@ -1042,5 +1042,12 @@ async function startServer() {
 module.exports = app;
 
 if (module === require.main) {
-	startServer();
+	startServer().catch(err => {
+		console.error(
+			"Unexpected error occured while starting master, please report\n"+
+			"it to https://github.com/clusterio/factorioClusterio/issues"
+		);
+		console.error(err);
+		return shutdown();
+	});
 }