Switching to NuGet Ardalis.Specifications (#389)

- updating to use Ardalis.Specifications package as it is maintained and has a more robust implementation
- Removing all custom specification implementation
- Updating unit tests

src/ApplicationCore/Interfaces/IAsyncRepository.cs

@@ -1,4 +1,5 @@
-using Microsoft.eShopWeb.ApplicationCore.Entities;
+using Ardalis.Specification;
+using Microsoft.eShopWeb.ApplicationCore.Entities;
 using System.Collections.Generic;
 using System.Threading.Tasks;
 

src/ApplicationCore/Interfaces/IIncludeQuery.cs

@@ -1,16 +0,0 @@
-using Microsoft.eShopWeb.ApplicationCore.Helpers.Query;
-using System.Collections.Generic;
-
-namespace Microsoft.eShopWeb.ApplicationCore.Interfaces
-{
-    public interface IIncludeQuery
-    {
-        Dictionary<IIncludeQuery, string> PathMap { get; }
-        IncludeVisitor Visitor { get; }
-        HashSet<string> Paths { get; }
-    }
-
-    public interface IIncludeQuery<TEntity, out TPreviousProperty> : IIncludeQuery
-    {
-    }
-}

src/ApplicationCore/Interfaces/ISpecification.cs

@@ -1,20 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq.Expressions;
-
-namespace Microsoft.eShopWeb.ApplicationCore.Interfaces
-{
-    public interface ISpecification<T>
-    {
-        Expression<Func<T, bool>> Criteria { get; }
-        List<Expression<Func<T, object>>> Includes { get; }
-        List<string> IncludeStrings { get; }
-        Expression<Func<T, object>> OrderBy { get; }
-        Expression<Func<T, object>> OrderByDescending { get; }
-        Expression<Func<T, object>> GroupBy { get; }
-
-        int Take { get; }
-        int Skip { get; }
-        bool IsPagingEnabled { get;}
-    }
-}