Detect geo of server.

Using geolite2, we attempt to detect the continent of the server
and store the 'continent code' in the serverlist. This is reasonably
broad enough to help players in the client find truly "nearby" server.

The client will have to be changed to select a continent to change
ordering or filtering.

requirements.txt

@@ -1,2 +1,2 @@
 Flask>=0.10
-
+maxminddb-geolite2>=2018.703

server.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 import os, re, sys, json, time, socket
 from threading import Thread, RLock
+from geolite2 import geolite2
 
 from flask import Flask, request, send_from_directory
 
@@ -277,6 +278,18 @@ def asyncFinishThread(server):
 					% (server["ip"], server["address"], addresses))
 			return
 
+	reader = geolite2.reader()
+	try:
+		geo = reader.get(server["ip"])
+	except geoip2.errors.GeoIP2Error:
+		app.logger.warning("GeoIP lookup failure for %s." % (server["address"],))
+
+	if "continent" in geo and "code" in geo["continent"]:
+		server["geo_continent"] = geo["continent"]["code"]
+	else:
+		app.logger.warning("Unable to get GeoIP Continent data for %s."
+				% (server["address"],))
+
 	server["ping"] = serverUp(info[0])
 	if not server["ping"]:
 		app.logger.warning("Server %s:%d has no ping."