Always show package sources in Available and Updates tab.

Do not hide the package sources combo box in the Manage Packages dialog
when only on package source is defined.

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

@@ -21,7 +21,7 @@ namespace ICSharpCode.PackageManagement
 			: base(registeredPackageRepositories, packageViewModelFactory, taskFactory)
 		{
 			IsSearchable = true;
-			ShowPackageSources = registeredPackageRepositories.HasMultiplePackageSources;
+			ShowPackageSources = true;
 		}
 		
 		protected override void UpdateRepositoryBeforeReadPackagesTaskStarts()

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

@@ -26,7 +26,7 @@ namespace ICSharpCode.PackageManagement
 				taskFactory)
 		{
 			this.selectedProjects = new PackageManagementSelectedProjects(solution);
-			ShowPackageSources = registeredPackageRepositories.HasMultiplePackageSources;
+			ShowPackageSources = true;
 		}
 		
 		protected override void UpdateRepositoryBeforeReadPackagesTaskStarts()

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

@@ -221,13 +221,13 @@ namespace PackageManagement.Tests
 		}
 		
 		[Test]
-		public void ShowPackageSources_OnePackageSources_ReturnsFalse()
+		public void ShowPackageSources_OnePackageSources_ReturnsTrue()
 		{
 			CreateRegisteredPackageRepositories();
 			AddOnePackageSourceToRegisteredSources();
 			CreateViewModel(registeredPackageRepositories);
 			
-			Assert.IsFalse(viewModel.ShowPackageSources);
+			Assert.IsTrue(viewModel.ShowPackageSources);
 		}
 		
 		[Test]

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

@@ -251,13 +251,13 @@ namespace PackageManagement.Tests
 		}
 		
 		[Test]
-		public void ShowPackageSources_OnePackageSources_ReturnsFalse()
+		public void ShowPackageSources_OnePackageSources_ReturnsTrue()
 		{
 			CreateRegisteredPackageRepositories();
 			AddOnePackageSourceToRegisteredSources();
 			CreateViewModel(registeredPackageRepositories);
 			
-			Assert.IsFalse(viewModel.ShowPackageSources);
+			Assert.IsTrue(viewModel.ShowPackageSources);
 		}
 	}
 }