Use IMAGE:latest as cache-from source for non-master builds

See merge request !16

Non-master builds are not pushed, so we can only use the master builds
as cache.

Registrar list

See merge request !14

Emg db configuration

See merge request !12

https://github.com/moby/moby/pull/37872
this means, our containers will run out of memory anyway, as they are 
allowed to swap indefinitely and we have swap memory allowed on the 
machines

Update configurations

See merge request !11