Add translations and dialog box radio button
for exporting privaye key as JWK

Existing selector of the private key format needs
to handle JWK. JWK supports aside of RSA and EdDSA
subset of EC curves. Passing just KeyPairType is not
sufficient, so this dialog now uses PrivateKey instance
to decide which output formats should be enabled
This is part of (kaikramer#438)

Reuse existing KSE utility code in JWK public key exporter.
Extract JWK common code that is shared by the public and
private key exporters

This is part of (kaikramer#438)

This is part of (kaikramer#438)

This is part of (kaikramer#438)

Export instances of RSAPrivateCrtKey as JWK

This is part of (kaikramer#438)

Export instances of ECPrivateKey as JWK

This is part of (kaikramer#438)

provide static method JwkPublicKeyExporter.isPublicKeyTypeExportable
which uses existing KSE functionality to check if key type
can be exported to Jwk, without creating instance of the JwkPublicKeyExporter class