ALF-10771: adding validation to schema compare tool

Added support to DbObjects to accept visitors
Added ValidatingVisitor to invoke suitable validator on each DbObject
Added NameValidator and NullValidator to operate on DbObject types
Added test suites



git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@31494 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/util/schemacomp/model/DbObject.java

@@ -18,6 +18,7 @@
  */
 package org.alfresco.util.schemacomp.model;
 
+import org.alfresco.util.schemacomp.DbObjectVisitor;
 import org.alfresco.util.schemacomp.DiffContext;
 import org.alfresco.util.schemacomp.Differences;
 import org.alfresco.util.schemacomp.Result.Strength;
@@ -60,4 +61,13 @@ public interface DbObject
      * @param ctx The DiffContext
      */
     void diff(DbObject right, DiffContext ctx, Strength strength);
+    
+    
+    /**
+     * Allows a visitor to be invoked against this DbObject. Implementations should ensure that child
+     * objects are visited first (by calling accept on them) before invoking the visitor on itself.
+     * 
+     * @param visitor
+     */
+    void accept(DbObjectVisitor visitor);
 }