Unattended auto-update confirmed working on EO2

What's Changed

• Judge video health by pixels, not only by callbacks by @aphex3k in #72
• Let a frame with no brightness button set its brightness floor by @aphex3k in #74
• Make a lost backlight level impossible to mistake for a chosen one by @aphex3k in #76
• Write a diagnostics report when the frame decides to reboot itself by @aphex3k in #78
• Speak the protocol adbd actually answers (fourcc tags, byte-sum checksum) by @aphex3k in #79
• Add the root certificates their 2013 ROM never shipped by @aphex3k in #80

Full Changelog: v2.0.0.13...v2.0.0.14