add a few jar attributes (#2736)
add a few jar attributes (#2736)

This allow in particular to use `getImplementationVersion()`: https://docs.oracle.com/javase/7/docs/api/java/lang/Package.html#getImplementationVersion()
apollographql/apollo-android,apollostack/apollo-android,apollographql/apollo-android,apollographql/apollo-android,apollostack/apollo-android,apollostack/apollo-android