Fix long standing bug where extra nodes in data.yml would be created

There was a bug where you would "randomly" get extra nodes in your
data.yml like jailnamecells, this caused problems earlier which was
avoided by not loading invalid jails but now the real issue is fixed and
those extra nodes shouldn't appear again.

src/main/java/com/graywolf336/jail/JailIO.java

@@ -1157,7 +1157,7 @@ public class JailIO {
                 break;
             default:
                 if(flat != null) {
-                    flat.set("jails." + j.getName() + "cells." + c.getName(), null);
+                    flat.set("jails." + j.getName() + ".cells." + c.getName(), null);
 
                     try {
                         flat.save(new File(pl.getDataFolder(), "data.yml"));