[System/SR] Brings some strings from .NET Core

Used the following script to do this:

var d = XDocument.Load ("Strings.resx");
foreach (var j in d.XPathSelectElements ("/root/data")){ var v = j.XPathSelectElement ("value"); Console.WriteLine ("\tpublic const string {0}=\"{1}\";", j.Attribute ("name").Value, v.Value); }