build_apk.sh assumed pre-releases would be sorted towards the end,
but instead they end up at the front (sort -n) causing the api
selection loop to halt early.
bug: 19213196
Change-Id: I210a18c16e81880229f154c4613f8b97d90ac9bd
tested: on Linux.
Previously Android.mk only had a rule for the Flatbuffers test. There
is now an empty module definition so that flatbuffers can be included
as an Android module in other projects.
Additionally, android/jni/include.mk has been added which contains
some utility functions that can be used by projects using Flatbuffers
to generate header build rules and set up dependencies.
A sample project has been added to the samples directory to
demonstrate how to use flatbuffers with Android.
Tested by compiling Android project on Linux.
Change-Id: I25d6da40f6531777b22f7371187e0a2f4e903ad4