MultiDex support: now secondary dex'es are located directly in apk file,...

... not in assets (compatible with android.support.MultiDex)

To make this work one should add these lines to main-dex-list file:
android/support/multidex/MultiDex.class
android/support/multidex/MultiDex$V4.class
android/support/multidex/MultiDex$V14.class
android/support/multidex/MultiDex$V19.class
android/support/multidex/MultiDexApplication.class
android/support/multidex/MultiDexExtractor.class
android/support/multidex/MultiDexExtractor$1.class
android/support/multidex/ZipUtil.class
android/support/multidex/ZipUtil$CentralDirectory.class