decryptFiles writes data it gets, even on error. Improve message.
decryptFiles writes data it gets, even on error. Improve message.

- summary shows "Decrypted ... file(s)" plus now "Problems with ... file(s)."
- non-Growl users also see file-level error message (in summary)
- also produce a message for NSException (in addition to GPGException)

strings changes:
- "Finished decrypting %i file(s)" -> "Decrypted %i file(s)."
- "Problems with %i file(s)." new
- "Decryption error" new for previously-silent NSException
- "An unexpected error occurred while decrypting." new for NSException

derikk/GPGServices,jasonchaffee/GPGServices