It's been over 3 years :)

The common module was designed to prevent the internal modules depending on the core plugin. With the introduction of localization, this overcomplication became ever more exacerbated.
Probably will play around a bit more to remove freshly introduced static abuse before release.
Closes #61

plugin/src/main/java/com/lishid/openinv/util/ConfigUpdater.java

@@ -59,6 +59,9 @@ public class ConfigUpdater {
                 if (version < 3) {
                     updateConfig2To3();
                 }
+                if (version < 4) {
+                    updateConfig3To4();
+                }
 
                 new BukkitRunnable() {
                     @Override
@@ -71,6 +74,17 @@ public class ConfigUpdater {
         }.runTaskAsynchronously(plugin);
     }
 
+    private void updateConfig3To4() {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
+                plugin.getConfig().set("notify", null);
+                plugin.getConfig().set("settings.locale", "en_US");
+                plugin.getConfig().set("config-version", 4);
+            }
+        }.runTask(plugin);
+    }
+
     private void updateConfig2To3() {
         new BukkitRunnable() {
             @Override