* +3.21 / -3.17
* remove unimplemented image_compress
* update TODO.md
* add IMPORTING.md
* remove deprecated get_latest_imported_tags
* set up gpio_pl06 for all aarch64
* recent cloud-init can use dhcpcd just fine
* always install non-busybox mount for 3.18+ (base/5.conf)
* tiny-cloud >= 3.1.0 does autodetection
* AWS & Azure images can use the same VHD format options
* nvme module is already enabled in cmdline/initramfs
* drop AWS NVMe core timeout setting for 3.21+
* switch GCP image format to "raw.tar.gz"
* enable GCP "gve" module on cmdline/initramfs
* drop setting "ntp_server", chrony will use default
* "generic" cloud should include all options for other clouds
* "generic" tiny-cloud starts with 3.21 (because of autodetection)
* move "sudo deprecated/removed" motd's out of version and into base configs
* cmdline console= for both x86_64 and aarch64 moved to base/1.conf
* ImageConfig.CONVERT_CMD resize raw image to 1 GiB before tar.gz
* ImageStorage.run() optionally supports shell string instead of individual args (for multi-step image conversions)
* don't disable getty on tty1 for those who need to login via VGA terminal (nocloud, etc?)