Move required files but 'nginx.tmpl' into a local 'app' folder and copy the
folder content into the image.
'nginx.tmpl' should be moved as well, but this is a breaking change for
configuration with a separate 'docker-gen' container.
This changes the base-image to the official nginx image,
reducing the virtual size of the image by approx 50%.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
