Allow key upgrades for devices when security level gets upgraded

If a device gets authorized in USER mode, but then the security level changes to SECURE, the device will NOT be automatically get authorized, because we can not verify the its identity via a key. When the user then manually authorizes the devices via the dbus Authorize method, and the device allows for it (stored and supports key verification), a new key will be generated and stored. See also issue #30 (closed)