Updating packaging commands to handle solution-less applications

If the solution is not found, don't NuGet-Install the package, but still NuGet-AddReference
Uninstallation deletes the module if there is no solution folder
Creating a specific ReferenceRepository implementation to remove the packages.config dependency

--HG--
branch : dev

src/Orchard.Web/Modules/Orchard.Packaging/Services/ExtensionReferenceRepository.cs

@@ -0,0 +1,62 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Xml.Linq;
+using NuGet;
+using Orchard.Environment.Extensions;
+
+
+namespace Orchard.Packaging.Services {
+    /// <summary>
+    /// This repository implementation informs about what packages are already installed.
+    /// </summary>
+    public class ExtensionReferenceRepository : PackageRepositoryBase {
+        private readonly IExtensionManager _extensionManager;
+        
+        public ExtensionReferenceRepository(IProjectSystem project, IPackageRepository sourceRepository, IExtensionManager extensionManager) {
+            if (project == null) {
+                throw new ArgumentNullException("project");
+            }
+            if (sourceRepository == null) {
+                throw new ArgumentNullException("sourceRepository");
+            }
+            if (extensionManager == null) {
+                throw new ArgumentNullException("extensionManager");
+            }
+            Project = project;
+            SourceRepository = sourceRepository;
+            _extensionManager = extensionManager;
+        }
+
+        private IProjectSystem Project {
+            get;
+            set;
+        }
+
+        private IPackageRepository SourceRepository {
+            get;
+            set;
+        }
+
+        public override IQueryable<IPackage> GetPackages() {
+            IEnumerable<IPackage> packages;
+
+            packages = from extension in _extensionManager.AvailableExtensions()
+                       let id = "Orchard." + extension.ExtensionType + "." + extension.Name
+                       let version = Version.Parse(extension.Version)
+                       let package = SourceRepository.FindPackage(id, version)
+                       where package != null
+                       select package;
+
+            return packages.AsQueryable();
+        }
+
+        public override void AddPackage(IPackage package) {
+        }
+
+        public override void RemovePackage(IPackage package) {
+        }
+    }
+}