Implement /data/.halium-rootfs install layout
The rootfs folder should be transferred using rsync, as described here: https://ptspts.blogspot.de/2015/03/how-to-use-rsync-over-adb-on-android.html. RSync makes updating the rootfs really fast, and reduces the writes to the internal storage. Static rsync builds are already available: https://github.com/JBBgameich/rsync-static/releases