Add version 6.0.0

Author: jdconrad

core/src/main/java/org/elasticsearch/Version.java

@@ -118,6 +118,9 @@ public class Version implements Comparable<Version> {
     public static final int V_6_0_0_rc2_ID = 6000052;
     public static final Version V_6_0_0_rc2 =
         new Version(V_6_0_0_rc2_ID, org.apache.lucene.util.Version.LUCENE_7_0_1);
+    public static final int V_6_0_0_ID = 6000099;
+    public static final Version V_6_0_0 =
+        new Version(V_6_0_0_ID, org.apache.lucene.util.Version.LUCENE_7_0_1);
     public static final int V_6_1_0_ID = 6010099;
     public static final Version V_6_1_0 =
         new Version(V_6_1_0_ID, org.apache.lucene.util.Version.LUCENE_7_1_0);
@@ -143,6 +146,8 @@ public static Version fromId(int id) {
                 return V_7_0_0_alpha1;
             case V_6_1_0_ID:
                 return V_6_1_0;
+            case V_6_0_0_ID:
+                return V_6_0_0;
             case V_6_0_0_rc2_ID:
                 return V_6_0_0_rc2;
             case V_6_0_0_beta2_ID: