zip command added

Install the Debian zip package so that downloads of whole albums as zip files are supported.
See #178 / #84

docker/Dockerfile

@@ -4,6 +4,7 @@ MAINTAINER CYOSP <cyosp@cyosp.com>
 RUN DEBIAN_FRONTEND=noninteractive apt update && apt upgrade -yq && apt install -yq \
 	--no-install-recommends \
 	ca-certificates \
+	zip \
 	git \
 	nginx \
 	php-fpm \
@@ -35,4 +36,4 @@ ADD supervisor.conf /etc/supervisor/conf.d/photoshow.conf
 VOLUME ["/opt/PhotoShow", "/var/log"]
 EXPOSE 80
 
-CMD /usr/bin/supervisord
+CMD /usr/bin/supervisord