Add android handler for (.so + Java) apps and a "device_name" example.

This patch adds a handler for Mojo apps composed of native and Java code on
Android. The handler bootstraps execution of the application so that the native
part can call the Java library.

A "device_name" example is also added to illustrate usage.

BUG=436508
R=cjhopman@chromium.org, qsr@chromium.org

Review URL: https://codereview.chromium.org/754013003