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/app/build.gradle

@@ -1,12 +1,12 @@
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion 26
+    compileSdkVersion 28
     buildToolsVersion '28.0.3'
 
     defaultConfig {
-        minSdkVersion 15
-        targetSdkVersion 15
+        minSdkVersion 16
+        targetSdkVersion 28
     }
 
     buildTypes {
@@ -23,5 +23,5 @@ android {
 }
 
 dependencies {
-    compile 'com.android.support:support-v4:26.1.0'
+    compile 'com.android.support:support-v4:28.0.0'
 }