Update Android Apps to use gradle

platform_tools/android/app/project.properties

Index: platform_tools/android/app/project.properties
diff --git a/platform_tools/android/app/project.properties b/platform_tools/android/app/project.properties
deleted file mode 100644
index 4ab125693c7c484a0252ee7eca9616e0f9b1ac67..0000000000000000000000000000000000000000
--- a/platform_tools/android/app/project.properties
+++ /dev/null
@@ -1,14 +0,0 @@
-# This file is automatically generated by Android Tools.
-# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
-#
-# This file must be checked in Version Control Systems.
-#
-# To customize properties used by the Ant build system edit
-# "ant.properties", and override values to adapt the script to your
-# project structure.
-#
-# To enable ProGuard to shrink and obfuscate your code, uncomment this (available properties: sdk.dir, user.home):
-#proguard.config=${sdk.dir}/tools/proguard/proguard-android.txt:proguard-project.txt
-
-# Project target.
-target=android-19