Add dockerfile to create an official docker image (#720)

.dockerignore

@@ -0,0 +1,8 @@
+.git
+cache/*
+DEBUG
+Dockerfile
+whitelist.txt
+phpcs.xml
+CHANGELOG.md
+CONTRIBUTING.md

Dockerfile

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+FROM ulsmith/alpine-apache-php7
+
+COPY ./ /app/public/
+
+RUN chown -R apache:root /app/public