Throwback Operator Firmware 2.0

Massive improvement to playback speed, accuracy and stability.
Tentative tests seem to show that the frequent SD card boot-loop has also been fixed by these changes.

Updates to existing units are strongly recommended.

Throwback Operator Firmware 1.1

• New watchdog timer that automatically resets the MCU should the unit hang
• New SD initialization code
• Fixed issue with MacOS placing metafiles on the SD card
• Fixed issue with using "next" button on last file causing MCU to hang

Throwback Operator Firmware 1.0

Merge branch 'master' of github.com:AidanHockey5/STM32_OPL3