Add Update All button to Manage Packages dialog.
Add Update All button to Manage Packages dialog.
Support updating all NuGet packages in solution from dialog
Refactor UpdatedPackagesViewModel.
Fix updated packages not being shown in dialog.

Updated packages were not being displayed in the
Manage Packages dialog when the solution was selected
and two or more projects had the same NuGet packages but
different versions.

http://nuget.codeplex.com/workitem/3034
Fix Include Prerelease checkbox missing from Updates tab.
Clear dialog error messages when updating all NuGet packages.
Update installed NuGet packages after updating all packages in dialog.
Refresh updated NuGet packages after updating in dialog.