Add YUNMAI LBM & visceral fat value. (#522)

* Add YUNMAI LBM value

this scale machine just use `weight - fat` formula

* Initial implement YunmaiLib.getVisceralFat

a return value range is 1 to 30
an original app use `floor` calculation to last value and return the integer value.
it's a different part.

android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiSE_Mini.java

@@ -145,6 +145,8 @@ public class BluetoothYunmaiSE_Mini extends BluetoothCommunication {
                 scaleBtData.setMuscle(yunmaiLib.getMuscle(bodyFat));
                 scaleBtData.setWater(yunmaiLib.getWater(bodyFat));
                 scaleBtData.setBone(yunmaiLib.getBoneMass(scaleBtData.getMuscle(), weight));
+                scaleBtData.setLbm(yunmaiLib.getLeanBodyMass(weight, bodyFat));
+                scaleBtData.setVisceralFat(yunmaiLib.getVisceralFat(bodyFat, scaleUser.getAge()));
             } else {
                 Timber.e("body fat is zero");
             }

android_app/app/src/main/java/com/health/openscale/core/bluetooth/lib/YunmaiLib.java

@@ -79,4 +79,48 @@ public class YunmaiLib {
 
         return boneMass;
     }
+
+    public float getLeanBodyMass(float weight, float bodyFat) {
+        if (bodyFat < 5.0f || bodyFat > 75.0f) {
+            return 0.0f;
+        }
+        return weight * (100.0f - bodyFat) / 100.0f;
+    }
+
+    public float getVisceralFat(float bodyFat, int age) {
+        float f = (bodyFat < 5.0f || bodyFat > 75.0f) ? 0.0f : bodyFat;
+        int a = (age < 18 || age > 120) ? 18 : age;
+
+        if (sex == 1) {
+            if (a < 40) {
+                f -= 21.0f;
+            } else if (a < 60) {
+                f -= 22.0f;
+            } else {
+                f -= 24.0f;
+            }
+        } else {
+            if (a < 40) {
+                f -= 34.0f;
+            } else if (a < 60) {
+                f -= 35.0f;
+            } else {
+                f -= 36.0f;
+            }
+        }
+
+        float d = sex == 1 ? 1.4f : 1.8f;
+        if (f > 0.0f) {
+            d = 1.1f;
+        }
+
+        float vf = (f / d) + 9.5f;
+        if (vf < 1.0f) {
+            return 1.0f;
+        }
+        if (vf > 30.0f) {
+            return 30.0f;
+        }
+        return vf;
+    }
 }