Command::Private:
* Add two constructors for commands that are independent of
  KeyListController, but that may set a parent widget (e.g. for dialogs
  shown by the commands)
* Simplify member initialization

CardCommand:
* Remove methods initially duplicated from Command
* Remove empty default implementation of doCancel()

AuthenticatePIVCardApplicationCommand, ChangePinCommand,
PIVGenerateCardKeyCommand, SetPIVCardApplicationAdministrationKeyCommand:
* Implement doCancel()
* Adjust some calls of methods of super class

CertificateToPIVCardCommand, KeyToCardCommand:
* Derive from CardCommand instead of Command
* Remove serialNumber member, get serial number from super class

ImportCertificateFromDataCommand:
* Add mId member to allow overriding the hard-coded id ("Notepad")

ImportCertificateFromPIVCardCommand:
* Derive from CardCommand instead of ImportCertificatesCommand
* Use ImportCertificateFromDataCommand internally
* Implement doCancel()

GnuPG-bug-id: 5066