Add Mass.Grain, SpecificEnergy.BtuPerPound (#582)

Author: mp9007

Common/UnitDefinitions/Mass.json

@@ -165,6 +165,20 @@
           "Abbreviations": [ "cwt" ]
         }
       ]
+    },
+    {
+      "SingularName": "Grain",
+      "PluralName": "Grains",
+      "FromUnitToBaseFunc": "x/15432.358352941431",
+      "FromBaseToUnitFunc": "x*15432.358352941431",
+      "XmlDocSummary": "A grain is a unit of measurement of mass, and in the troy weight, avoirdupois, and Apothecaries' system, equal to exactly 64.79891 milligrams.",
+      "XmlDocRemarks": "https://en.wikipedia.org/wiki/Grain_(unit)",
+      "Localization": [
+        {
+          "Culture": "en-US",
+          "Abbreviations": [ "gr" ]
+        }
+      ]
     }
   ]
 }

Common/UnitDefinitions/SpecificEnergy.json

@@ -46,6 +46,18 @@
           "Abbreviations": [ "Wh/kg" ]
         }
       ]
+    },
+    {
+      "SingularName": "BtuPerPound",
+      "PluralName": "BtuPerPound",
+      "FromUnitToBaseFunc": "x*2326.000075362",
+      "FromBaseToUnitFunc": "x/2326.000075362",
+      "Localization": [
+        {
+          "Culture": "en-US",
+          "Abbreviations": [ "btu/lb" ]
+        }
+      ]
     }
 
   ]

UnitsNet.Tests/CustomCode/MassTests.cs

@@ -33,6 +33,8 @@ public class MassTests : MassTestsBase
 
         protected override double DecigramsInOneKilogram => 1E4;
 
+        protected override double GrainsInOneKilogram => 15432.358352941431d;
+
         protected override double GramsInOneKilogram => 1E3;
 
         protected override double HectogramsInOneKilogram => 10;

UnitsNet.Tests/CustomCode/SpecificEnergyTests.cs

@@ -28,6 +28,7 @@ public class SpecificEnergyTests : SpecificEnergyTestsBase
         protected override double JoulesPerKilogramInOneJoulePerKilogram => 1e0;
         protected override double KilojoulesPerKilogramInOneJoulePerKilogram => 1e-3;
         protected override double MegajoulesPerKilogramInOneJoulePerKilogram => 1e-6;
+        protected override double BtuPerPoundInOneJoulePerKilogram => 4.299226e-4;
         protected override double CaloriesPerGramInOneJoulePerKilogram => 2.3900573613766730401529636711281e-4;
         protected override double KilocaloriesPerGramInOneJoulePerKilogram => 2.3900573613766730401529636711281e-7;
         protected override double WattHoursPerKilogramInOneJoulePerKilogram => 2.77777778e-4;
@@ -69,4 +70,4 @@ public void SpecificEnergyTimesBrakeSpecificFuelConsumptionEqualsEnergy()
             Assert.Equal(200d, value);
         }
     }
-}
+}