Export Certificate as PKCS12/PFX Does Not Provide Passphrase Encoding.

According to PCKS #12 we should have a password to protect the private key that is exported with the cert. Currently the key vault gives you a warning during export/download that no password is used, however it doesn't provide the capability to provide a passphrase.

Strangely enough the API Manager and other Azure Resources require imported certificates to have a passphrase. This makes the two services fairly incompatible.

It would be good if Certificates exported from KeyVaults have the option to protect the private key with a passphrase as per PKCS #12