upgrading build tools and NuGet packages. switching to Xamarin's Biometric Bindings (even though this reverts from 1.0.1 to 1.0.0) because of build issues/incompatibilities

src/java/android-filechooser-AS/build.gradle

@@ -1,20 +1,30 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
+
 buildscript {
     repositories {
         jcenter()
+        maven {
+            url 'https://maven.google.com/'
+            name 'Google'
+        }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.1.3'
+        classpath 'com.android.tools.build:gradle:3.3.2'
+
+        // NOTE: Do not place your application dependencies here; they belong
+        // in the individual module build.gradle files
+        //classpath 'com.getkeepsafe.dexcount:dexcount-gradle-plugin:0.7.1'
     }
+
 }
+
 allprojects {
     repositories {
         jcenter()
+        google()
     }
 }
 
-dependencies {
+task clean(type: Delete) {
+    delete rootProject.buildDir
 }
-android {
-    buildToolsVersion '23.0.2'
-}