Replace custom AES implementation with CommonCrypto calls
Refactor AES decryption stream

* Decryption stream init now only needs AES encryption strength, not entire AES extra field.

* Fix read not starting on a block boundary causing gap in keystream.

* Fix password error still allowing stream to open.

* Remove extraneous NSData allocations during init.

* Unify counter and nonce.
Fix encrypted zip files included in zipping tests