Py-minisign

The return code is now `1` on verification/password error, and `2` for system errors.

Bug fix: `-p` and `-V` could not be used together. It has been fixed.

New option: `-o`, that can be combined with `-V` in order to send the content of the signed file to `stdout` after successful verification.

New switch: `-Q`, to display only the trusted comment (after verification)