Separate reboot and no-reboot scenarios

Refactor update callback method into a private method
so it can be used by different update related messages.

Differenciate between reboot and no-reboot signals, using
two separate callbacks.

Update dbus signal information.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Release 0.1.0-1

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>