Improve error message when commands fail to be added and make commands using the new system check for masking (#1404)

* Improve error message when command already exists

* Add app's name to the message

* Add app name to any command load failure and fix commands from new system masking existing ones

* Fix duplicated app name in an error

* Update to recent snapshot changes

src/main/java/carpet/script/CarpetScriptServer.java

@@ -295,9 +295,9 @@ public class CarpetScriptServer extends ScriptServer
         //addEvents(source, name);
         String action = (installer!=null)?(reload?"reinstalled":"installed"):(reload?"reloaded":"loaded");
 
-        
+        String finalName = name;
         Boolean isCommandAdded = newHost.addAppCommands(s -> {
-            if (!isRuleApp) Messenger.m(source, s);
+            if (!isRuleApp) Messenger.m(source, Messenger.c("r Failed to add app '" + finalName + "': ", s));
         });
         if (isCommandAdded == null) // error should be dispatched
         {