Added screen statistic sensors and new buttons

[paviro]

This adds:

• Better initial display refresh
• Reboot and shutdown button
• Update screen script and button
• Sensor for last screen update and total updates

Please build and check before merging as I copied the changes from my quite heavily modified version.

[Madelena]

This is awesome! Thanks so much for this @paviro !!

[paviro]

Very welcome!