PrimeOrderCalculator converted to a template.

PerfectNumbers.Core/UInt128Numbers.cs

@@ -5,6 +5,7 @@ namespace PerfectNumbers.Core
     public static class UInt128Numbers
     {
         public static readonly UInt128 Two = 2UL;
+        public static readonly UInt128 Three = 3UL;
         public static readonly UInt128 Four = 4UL;
         public static readonly UInt128 SixtyFour = 64UL;
         public static readonly UInt128 OneHundredTwentySeven = 127UL;