Adding migrations for v6 upgrades.

Updating and testing migrations.

src/Umbraco.Core/Persistence/DatabaseModelDefinitions/ConstraintDefinition.cs

@@ -12,6 +12,7 @@ namespace Umbraco.Core.Persistence.DatabaseModelDefinitions
         private ConstraintType constraintType;
         public bool IsPrimaryKeyConstraint { get { return ConstraintType.PrimaryKey == constraintType; } }
         public bool IsUniqueConstraint { get { return ConstraintType.Unique == constraintType; } }
+        public bool IsNonUniqueConstraint { get { return ConstraintType.NonUnique == constraintType; } }
 
         public string SchemaName { get; set; }
         public string ConstraintName { get; set; }

src/Umbraco.Core/Persistence/DatabaseModelDefinitions/ConstraintType.cs

@@ -3,6 +3,7 @@ namespace Umbraco.Core.Persistence.DatabaseModelDefinitions
     public enum ConstraintType
     {
         PrimaryKey,
-        Unique
+        Unique,
+        NonUnique
     }
 }