[HEX-2014] Generated model provides UUID call.

The common interface `IGeneratedModel` now provides
the method 'getUUID' providing a string derived
from model's UniqueId#id.

src/main/java/water/Model.java

@@ -1,26 +1,19 @@
 package water;
 
+import static water.util.JCodeGen.toStaticVar;
 import hex.ConfusionMatrix;
 import hex.VarImp;
+
+import java.util.*;
+
 import javassist.*;
 import water.api.*;
 import water.api.Request.API;
-import water.fvec.Chunk;
-import water.fvec.Frame;
-import water.fvec.TransfVec;
-import water.fvec.Vec;
+import water.fvec.*;
 import water.serial.AutoBufferSerializer;
 import water.util.*;
 import water.util.Log.Tag.Sys;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Date;
-import java.util.HashMap;
-
-import static water.util.JCodeGen.toStaticVar;
-import static water.util.Utils.contains;
-
 /**
  * A Model models reality (hopefully).
  * A model can be used to 'score' a row, or a collection of rows on any
@@ -658,6 +651,9 @@ protected SB toJavaSuper( SB sb ) {
     sb.ii(1);
     sb.i().p("public String[]   getNames() { return NAMES; } ").nl();
     sb.i().p("public String[][] getDomainValues() { return DOMAINS; }").nl();
+    String uuid = this.uniqueId != null ? this.uniqueId.getId() : this._key.toString();
+    sb.i().p("public String     getUUID() { return ").ps(uuid).p("; }").nl();
+
     return sb;
   }
   private SB toJavaNAMES( SB sb ) { return JCodeGen.toStaticVar(sb, "NAMES", _names, "Names of columns used by model."); }

src/main/java/water/genmodel/IGeneratedModel.java

@@ -6,6 +6,9 @@
  * A generic interface to access generated models.
  */
 public interface IGeneratedModel {
+    /** Returns model's unique identifier. */
+    public String getUUID();
+
     /** Returns number of columns used as input for training (i.e., exclude response column). */
     public int getNumCols();