Get Android build working

mobile/android/app/local.properties

@@ -0,0 +1,8 @@
+## This file must *NOT* be checked into Version Control Systems,
+# as it contains information specific to your local configuration.
+#
+# Location of the SDK. This is only used by Gradle.
+# For customization when using a Version Control System, please read the
+# header note.
+#Sat Mar 31 13:51:09 PDT 2018
+sdk.dir=/Users/john/Library/Android/sdk