Automatically calculate certificate thumbprint

`sign` requires a certificate thumbprint to be explicitly specified in the command line:

```
Usage:
sign code certificate-store ... [options]

Arguments:
File(s) to sign.

Options:
-cfp, --certificate-fingerprint (REQUIRED) SHA fingerprint used to identify a certificate.
-cf, --certificate-file PFX, P7B, or CER file containing a certificate and potentially a private key.
-p, --password Password for certificate file.
-csp, --crypto-service-provider Cryptographic Service Provider containing the private key container. Requires /k and optionally /km.
-k, --key-container Private key container name.
```

However, when a certificate file is specified with `-cf` (` --certificate-file`) option, it already has all the information to calculate its thumbprint. In this case, `-cfp` (`--certificate-fingerprint`) option should not be obligatory.

The current behavior requires a user to always specify `-cfp` (`--certificate-fingerprint`) option, even when the certificate file is specified explicitly. This adds certain frictions to `sign` usage as the user now has to manually extract/calculate the certificate fingerprint, even when it isn't strictly needed and can be extracted from the specified certificate file automatically.

sign version: 0.9.1-beta.25379.1+ba6e717abf74a693f0f9c5e891c0e3ef624956b3