Adds the foundation for the repository implementation with abstract Repository, Unit Of Work and Cache provider.

Adding the Query object implementation.
Adds the ModelDtoMapper, which is still a WIP.
Adds the initial implementation of the IContentRepository with dependencies.

src/Umbraco.Core/Persistence/UnitOfWork/IUnitOfWork.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Umbraco.Core.Persistence.UnitOfWork
+{
+    public interface IUnitOfWork : IDisposable
+    {
+        void Commit();
+        Database Storage { get; } //TODO consider replacing 'Database' with a datastorage adapter, so there is no direct dependency on PetaPoco
+    }
+}

src/Umbraco.Core/Persistence/UnitOfWork/IUnitOfWorkProvider.cs

@@ -0,0 +1,7 @@
+namespace Umbraco.Core.Persistence.UnitOfWork
+{
+    public interface IUnitOfWorkProvider
+    {
+        IUnitOfWork GetUnitOfWork();
+    }
+}