RemoteLinux: More preparations for introducing an abstract device class.

- Introduce clone() method.
- Rename "osType" to "type" and "deviceType" to "machineType".
- Move machine type display out of generic settings widget.
- Put only immutable attributes into the device constructor and set the
others via setters. As part of this, also give the
SshConnectionParameters a default proxy type. The necessity to give one
to the constructor explicitly was for historical reasons.

Change-Id: I84757b1b2d6371544b9ab1f3290973e5498176ce
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>