Remove All from package source combo box when only one source.

Disabled package sources were being counted when deciding whether to add All
to the combo box in the Manage Packages dialog.

src/AddIns/Misc/PackageManagement/Project/Src/PackagesViewModel.cs

@@ -345,7 +345,7 @@ namespace ICSharpCode.PackageManagement
 				foreach (PackageSource packageSource in registeredPackageRepositories.PackageSources.GetEnabledPackageSources()) {
 					yield return packageSource;
 				}
-				if (registeredPackageRepositories.PackageSources.HasMultiplePackageSources) {
+				if (registeredPackageRepositories.PackageSources.HasMultipleEnabledPackageSources) {
 					yield return RegisteredPackageSourceSettings.AggregatePackageSource;
 				}
 			}

src/AddIns/Misc/PackageManagement/Project/Src/RegisteredPackageRepositories.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.PackageManagement
 		}
 		
 		public bool HasMultiplePackageSources {
-			get { return registeredPackageSources.HasMultiplePackageSources; }
+			get { return registeredPackageSources.HasMultipleEnabledPackageSources; }
 		}
 		
 		public PackageSource ActivePackageSource {

src/AddIns/Misc/PackageManagement/Project/Src/RegisteredPackageSources.cs

@@ -48,8 +48,8 @@ namespace ICSharpCode.PackageManagement
 			get { return Count == 0; }
 		}
 		
-		public bool HasMultiplePackageSources {
-			get { return Count > 1; }
+		public bool HasMultipleEnabledPackageSources {
+			get { return GetEnabledPackageSources().Count() > 1; }
 		}
 		
 		public IEnumerable<PackageSource> GetEnabledPackageSources()

src/AddIns/Misc/PackageManagement/Test/Src/RegisteredPackageRepositoriesTests.cs

@@ -80,6 +80,7 @@ namespace PackageManagement.Tests
 		{
 			CreateRegisteredPackageRepositories();
 			packageSourcesHelper.AddOnePackageSource();
+			
 			bool result = registeredRepositories.HasMultiplePackageSources;
 			
 			Assert.IsFalse(result);
@@ -90,11 +91,24 @@ namespace PackageManagement.Tests
 		{
 			CreateRegisteredPackageRepositories();
 			packageSourcesHelper.AddTwoPackageSources();
+			
 			bool result = registeredRepositories.HasMultiplePackageSources;
 			
 			Assert.IsTrue(result);
 		}
 		
+		[Test]
+		public void HasMultiplePackageSources_TwoPackageSourcesButOneIsDisabled_ReturnsFalse()
+		{
+			CreateRegisteredPackageRepositories();
+			packageSourcesHelper.AddTwoPackageSources();
+			packageSourcesHelper.RegisteredPackageSources[0].IsEnabled = false;
+			
+			bool result = registeredRepositories.HasMultiplePackageSources;
+			
+			Assert.IsFalse(result);
+		}
+		
 		[Test]
 		public void ActivePackageSource_TwoPackageSources_ByDefaultReturnsFirstPackageSource()
 		{