Adding A/in² and A/ft² for ElectricCurrentDensity. Also adding BaseUnits while I'm in there (#641)

Author: tmilnthorp

Common/UnitDefinitions/ElectricCurrentDensity.json

@@ -11,6 +11,10 @@
     {
       "SingularName": "AmperePerSquareMeter",
       "PluralName": "AmperesPerSquareMeter",
+      "BaseUnits": {
+        "L": "Meter",
+        "I": "Ampere"
+      },
       "FromUnitToBaseFunc": "x",
       "FromBaseToUnitFunc": "x",
       "Localization": [
@@ -19,6 +23,38 @@
           "Abbreviations": [ "A/m²" ]
         }
       ]
+    },
+    {
+      "SingularName": "AmperePerSquareInch",
+      "PluralName": "AmperesPerSquareInch",
+      "BaseUnits": {
+        "L": "Inch",
+        "I": "Ampere"
+      },
+      "FromUnitToBaseFunc": "x * 1.5500031000062000e3",
+      "FromBaseToUnitFunc": "x / 1.5500031000062000e3",
+      "Localization": [
+        {
+          "Culture": "en-US",
+          "Abbreviations": [ "A/in²" ]
+        }
+      ]
+    },
+    {
+      "SingularName": "AmperePerSquareFoot",
+      "PluralName": "AmperesPerSquareFoot",
+      "BaseUnits": {
+        "L": "Foot",
+        "I": "Ampere"
+      },
+      "FromUnitToBaseFunc": "x * 1.0763910416709722e1",
+      "FromBaseToUnitFunc": "x / 1.0763910416709722e1",
+      "Localization": [
+        {
+          "Culture": "en-US",
+          "Abbreviations": [ "A/ft²" ]
+        }
+      ]
     }
   ]
 }

UnitsNet.Tests/CustomCode/ElectricCurrentDensityTests.cs

@@ -28,5 +28,7 @@ namespace UnitsNet.Tests.CustomCode
     public class ElectricCurrentDensityTests : ElectricCurrentDensityTestsBase
     {
         protected override double AmperesPerSquareMeterInOneAmperePerSquareMeter => 1;
+        protected override double AmperesPerSquareInchInOneAmperePerSquareMeter => 6.4516e-4;
+        protected override double AmperesPerSquareFootInOneAmperePerSquareMeter => 9.290304e-2;
     }
 }