primarily performance and correctness lint fixes

This is a long one, but it takes care of a decent amount of annoyingness and makes our code more obvious and explicit. Also cleaned up unused resources that have been sitting around for quite a while.

Performance improvements are largely around flattening layouts and minimizing memory leaks, correctness about hardcoded strings and explicit annotations for using APIs only available on certain platforms.

Went from 349 errors and 565 warnings to 2 errors and 62 warnings (the two errors will be corrected once translations are imported).
Right now, this is how TextSecure behaves as it's implicitly true. Right now, the only way people can backup properly is with something like adb backup since our solution is broken. I'm proposing we keep this at true, fix our encrypted/plaintext export, then set to false since this causes problems with push registration.