Cleanup

* Please do carefully review the changes proposed here. Everything still builds afterwards, and I'm pretty sure they're right, but I'm not very close to this code base any more.
* There might be other resources that can be removed--things present on the filesystem but not visible in Xcode. @dgoldman-ebay?
* If we remove the `__TIME__` hash from the version string (why not just leave it unhashed?), then we can remove `CardIOString` altogether, I believe.
* I left in the device code that handles the 3GS, but I think that none of the iOS versions that we officially support will run on the 3GS. If that is so, then more of `CardIODevice` could go.
* The final commit in the PR depends on https://github.com/card-io/card.io-dmz/pull/2.