Splits logic for IPackageBuilder into ICreatedPackagesRepository and IInstalledPackagesRepository since it's nearly the same for both

src/Umbraco.Core/Packaging/IPackageDefinitionRepository.cs

@@ -0,0 +1,23 @@
+using System.Collections.Generic;
+using Umbraco.Core.Models.Packaging;
+
+namespace Umbraco.Core.Packaging
+{
+    /// <summary>
+    /// Defines methods for persisting package definitions to storage
+    /// </summary>
+    public interface IPackageDefinitionRepository
+    {
+        IEnumerable<PackageDefinition> GetAll();
+        PackageDefinition GetById(int id);
+        void Delete(int id);
+
+        /// <summary>
+        /// Persists a package definition to storage
+        /// </summary>
+        /// <returns>
+        /// true if creating/updating the package was successful, otherwise false
+        /// </returns>
+        bool SavePackage(PackageDefinition definition);
+    }
+}