Improve OS-integration features

[sassanh]

Based on the state of monitor/keyboard/mouse being connected to the pod or not and the features of these devices (for example monitor having speakers or not) and based on previous decisions of the user (for example whether they explicitly and intentionally disabled lightdm or not) we may have different reactions on the ubo-pod to:

1. Avoid the accessibility voice of piwiz when it is not needed (for example when user has not connected mouse/keyboard/monitor, it doesn't make sense to have the voice of piwiz)
2. Select correct audio output.
3. Avoid showing ubo-pod on the monitor.

These and probably some other issues need to be addressed by having better integration with the operating system.