Refactor multi-platform to not need multiple stage0

[raccube]

• Modified odroid partition layout to use a separate boot partition
• Added Raspberry Pi 4 support
• Added quiet to odroid boot command line
• Set init to systemd-init for odroid
• Set bootdelay to 0 in odroid U-Boot script

Closes #17 Closes #18

[trickeydan]

Fixes #17

[raccube]

This will also break CI due to the build.py arguments changing