Use best practices for Dockerfiles (#180)

web/Dockerfile

@@ -1,9 +1,10 @@
 FROM nginx:mainline
 
+# Remove default configuration and add our custom Nginx configuration files
 RUN rm /etc/nginx/conf.d/default.conf
 COPY ./mattermost /etc/nginx/sites-available/
 COPY ./mattermost-ssl /etc/nginx/sites-available/
 
-COPY docker-entry.sh /
-RUN chmod +x /docker-entry.sh
-ENTRYPOINT /docker-entry.sh
+# Add and setup entrypoint
+COPY entrypoint.sh /
+ENTRYPOINT ["/entrypoint.sh"]