Eclipse: Add place holder files for empty src directories.

Add place holder files to android/common/main/src and
android/premium/test/src. These directories are otherwise empty. The
Android build-chain reports a compiler error when the src directory does
not exist in an Android project. These place holder files help to avoid
such errors in a newly cloned repository.
Eclipse: Add the Google AdMob JAR file to the build classpath.

Add the Google AdMob JAR file to the build classpath for the
bbct-android-lite project.