update targetSdkVersion to 29 (Android 10/Q). Change canvas clipping in Soft keyboard to adhere to behavior changes in Android 10. Migrate to AndroidX. Migrate to using BiometricPrompt instead of FingerprintManager, keeping compatibility to SamsungPass API for devices like SGS5. Closes #795, should close #626, closes #910

src/BiometricBinding/Additions/AboutAdditions.txt

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+Additions allow you to add arbitrary C# to the generated classes
+before they are compiled.  This can be helpful for providing convenience
+methods or adding pure C# classes.
+
+== Adding Methods to Generated Classes ==
+
+Let's say the library being bound has a Rectangle class with a constructor
+that takes an x and y position, and a width and length size.  It will look like
+this:
+
+public partial class Rectangle
+{
+    public Rectangle (int x, int y, int width, int height)
+    {
+        // JNI bindings
+    }
+}
+
+Imagine we want to add a constructor to this class that takes a Point and
+Size structure instead of 4 ints.  We can add a new file called Rectangle.cs
+with a partial class containing our new method:
+
+public partial class Rectangle
+{
+    public Rectangle (Point location, Size size) :
+        this (location.X, location.Y, size.Width, size.Height)
+    {
+    }
+}
+
+At compile time, the additions class will be added to the generated class
+and the final assembly will a Rectangle class with both constructors.
+
+
+== Adding C# Classes ==
+
+Another thing that can be done is adding fully C# managed classes to the
+generated library.  In the above example, let's assume that there isn't a
+Point class available in Java or our library.  The one we create doesn't need
+to interact with Java, so we'll create it like a normal class in C#.
+
+By adding a Point.cs file with this class, it will end up in the binding library:
+
+public class Point
+{
+    public int X { get; set; }
+    public int Y { get; set; }
+}