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).
I missed that the verify array in the root build.gradle also included the library's dependencies. I'll take this out, but it does seem to me like the library, being a totally separate project theoretically, should verify its own dependencies without relying on the parent?