feat(router): image without development libraries to reduce the size

With this change the router is at least 60% smaller than the actual one.
The change was done in how the custom nginx is built. Using a intermediate image is possible to build nginx, compress the nginx installation directory and store in the image the tgz file. The real deis-router just copy the tgz from the other container and inject the tgz (with the rest of the current files). 
Because of this the router can use the ubuntu-debootstrap docker image.