Add icons and splashs for Android

mobile-config.js

public/images/logo/512x512.png

public/images/logo/android-hdpi.png

public/images/logo/android-mdpi.png

public/images/logo/android-xhdpi.png

public/images/logo/android-xxhdpi.png

public/images/logo/android-xxxhdpi.png

splash/android-land-hdpi.png

splash/android-land-ldpi.png

splash/android-land-mdpi.png

splash/android-land-xhdpi.png

splash/android-land-xxhdpi.png

splash/android-land-xxxhdpi.png

splash/android-port-hdpi.png

splash/android-port-ldpi.png

splash/android-port-mdpi.png

splash/android-port-xhdpi.png

splash/android-port-xxhdpi.png

splash/android-port-xxxhdpi.png

splash/android_base.png