Remove default php version from debian

[twisted1919]

I hit an issue where if i created a container based on FROM alterway/php:7.1-fpm and i then connect to it and type /usr/bin/php i get php 5.6 instead of 7.1. To get php 7.1 i have to either use php only or /usr/local/bin/php which is super confusing and took me few hours to figure out why i couldn't connect to mysql using PDO because it complained it can't find a valid driver.

My advice is to simply remove php 5.6 from the debian release: RUN apt-get -y purge php.* this way we will only have a single PHP version and there will be no confusion whatsoever.