Provide a base image for the CTP7 SD card
Description
Lately new SD cards for the CTP7 have been prepared by mirroring one from another working CPT7. This is not convenient and may not be possible in all situations. Additionally, it provides no documentation to reproduce the system.
Instead, we should provide a base image for the CTP7 SD card, updated whenever needed. That does not prevent - but simplifies - the writing of a proper documentation. In some way, it supersedes !167.