Provide a script to install Nuxeo packages at build time

The goal is to not rely on the docker-entrypoint.sh file to configure Nuxeo and install Nuxeo packages but on a specific script whose work is to handle Nuxeo packages installation at build time.
There is already a script (install-packages.sh) in the final Docker image, but it's to install packages without Connect. This script needs to be reworked to allow the installation of Nuxeo packages from Connect.

Usage would be:

/install-packages.sh [--connect-url <connecturl>] [--clid <clid>] <packagelist>

The script will take care of cleaning the created CLID and the nuxeo.conf modification from the image after the packages are installed.

When building a new Docker image from the nuxeo/nuxeo:11.x, the script could be used as:

FROM nuxeo/nuxeo:11.x
...
ARG NUXEO_INSTALL_CONNECT_URL
ARG NUXEO_INSTALL_CLID
RUN /install-packages.sh --connect-url $NUXEO_INSTALL_CONNECT_URL --clid $NUXEO_INSTALL_CLID /tmp/package.zip $CUSTOMER_PACKAGE
...