allow to retry after "error downloading distribution list from internet"

[SimonHeimberg]

When NOOBS lite fails to download the distribution list, the error dialogue can be closed (fixed since #101). But thereafter no actions are possible, since the os list is empty (obviously) and all buttons are disabled.

Suggestion:

• In this case, add a button to reload the distribution list from internet.
• Enable some buttons (wifi, help)
• Maybe generally an option to reboot

[procount]

Adding suggestion 1 to PINN as an experiment... (other 2 options already included in PINN)