Some refactoring / removed current test classes

src/opensesim/util/AssetVol.java

@@ -25,7 +25,7 @@
  */
 package opensesim.util;
 
-import opensesim.AbstractAsset;
+import opensesim.world.AbstractAsset;
 
 /**
  *

src/opensesim/util/IDGenerator.java

@@ -37,7 +37,7 @@ import java.util.Objects;
 public class IDGenerator {
     
     
-    public static class Id {
+    public static class Id implements Comparable<Id>{
         final Long value;
 
         public Id(String id) {
@@ -62,6 +62,15 @@ public class IDGenerator {
         public String toString() {
             return value.toString();
         }
+
+        @Override
+        public int compareTo(Id o) {
+            if (this.value>o.value)
+                return 1;
+            if (this.value<o.value)
+                return -1;
+            return 0;
+        }
         
         
     }