* Add pkg for System.Diagnostics.PerformanceCounter
This change adds System.Diagnostics.PerformanceCounter to the compat
pack.
* Add AllXamarinFrameworks to PerformanceCounter pkgproj
* Update PerformanceCounter pkgproj for xamarin/mono
* Change InboxOnTargetFramework to AllXamarinFrameworks
This meta-package will make it easier for .NET Core developers to add a set of
library packages to help them port code from .NET Framework to .NET Core.