Add the ability to quickly add a file to an Android backup

I killed off the Ant build system in favor of gradle.   It saves from manually having to download bountycastle and such manually while still not including the proprietary  .jar in the build system. If you don't like that part, but do like the addendum to add a new file to a backup, I can cherry-pick it.  If you don't like any of it, that's fine too =)  .. Just figured I'd throw this out there in case it was helpful for someone else.