Improve docker build to use hooks

Dockerfile

@@ -1,12 +1,30 @@
-FROM fguillot/alpine-nginx-php7
-
-COPY . /var/www/app
-COPY docker/kanboard/config.php /var/www/app/config.php
-COPY docker/crontab/cronjob.alpine /var/spool/cron/crontabs/nginx
-COPY docker/services.d/cron /etc/services.d/cron
-COPY docker/php/env.conf /etc/php7/php-fpm.d/env.conf
-
-RUN chown -R nginx:nginx /var/www/app/data /var/www/app/plugins
+FROM alpine:3.6
 
 VOLUME /var/www/app/data
 VOLUME /var/www/app/plugins
+
+EXPOSE 80
+
+ARG VERSION
+
+RUN apk update && \
+    apk add unzip nginx bash ca-certificates s6 curl ssmtp mailx php7 php7-phar php7-curl \
+    php7-fpm php7-json php7-zlib php7-xml php7-dom php7-ctype php7-opcache php7-zip php7-iconv \
+    php7-pdo php7-pdo_mysql php7-pdo_sqlite php7-pdo_pgsql php7-mbstring php7-session \
+    php7-gd php7-mcrypt php7-openssl php7-sockets php7-posix php7-ldap php7-simplexml && \
+    rm -rf /var/cache/apk/* && \
+    rm -rf /var/www/localhost && \
+    rm -f /etc/php7/php-fpm.d/www.conf
+
+RUN cd /tmp \
+    && curl -sL -o kb.zip https://github.com/kanboard/kanboard/archive/$VERSION.zip \
+    && unzip -qq kb.zip \
+    && cd kanboard-* \
+    && cp -R . /var/www/app \
+    && cd /tmp \
+    && rm -rf /tmp/kanboard-* /tmp/*.zip
+
+ADD docker/ /
+
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+CMD []