the nginx.repo file is copied in the container only if it is necessary

Added voms-clients-java

Provide two cases: one to install nginx httpg, one for nginx stable

Try to create two rpm, one for ngx with httpg patch, one for voms module

gitlab-ci and readme need to be updated

This script is used during the CI.

It is moved from .devocontainer to docker folder, probably this is not the correct place.

fix issue #19

This commit introduces the ngx-voms docker image, and modifies the CI
configuration to build the image.