Add Dockerfile based on php:7.1-apache image

[nolith]

Hello, I wanted to test CGP but not having any apache+PHP server available I made a Dockerfile.

I made a master build available at https://quay.io/repository/nolith/cgp

In general, if you want to build it yourself it's just

docker build -t cgp .

And then you can run it with

docker run --rm -p 8080:80 \
  -v /path/to/your/rdd:/var/lib/collectd/rrd \
  -v /usr/share/collectd:/usr/share/collectd:ro \
  cgp

and then open http://localhost:8080

[jrhunger]

Just a note for anyone else searching and finding this. You can go as new as php:7.2-apache but PCRE incompatible changes cause an issue starting at 7.3.