Upgrade dependencies and build system

This commit switches to use official Google NDK version 16 with packages
created/installed using android-crew-staging tool derived from CrystaX
project.

Change-Id: I248fef2a871e44375512dcbf15a5f3166c0ab5de
diff --git a/.gitmodules b/.gitmodules
index 96a2d18..62d1207 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -4,8 +4,9 @@
     branch = android
 [submodule "app/src/main/jni/ndn-cxx"]
     path = app/src/main/jni/ndn-cxx
-    url = https://github.com/cawka/ndn-cxx
+    url = https://github.com/named-data-mobile/ndn-cxx
     branch = 0.5.0-android-hotfix
 [submodule "app/src/main/jni/NFD"]
     path = app/src/main/jni/NFD
-    url = https://github.com/named-data/NFD
+    url = https://github.com/named-data-mobile/NFD
+    branch = master