Add hadolint

[ad-m]

I introduced the hadolint and adapted to its requirements. Before the changes, it reported the following errors:

./php-apache/base/Dockerfile:6 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
./php-apache/base/Dockerfile:7 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
./php-apache/base/Dockerfile:13 DL3008 Pin versions in apt get install. Instead of `apt-get install <package>` use `apt-get install <package>=<version>`
./php-apache/base/Dockerfile:24 SC2028 echo may not expand escape sequences. Use printf.
./php-apache/7.2/Dockerfile:6 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
./php-apache/7.2/Dockerfile:7 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
./php-apache/7.2/Dockerfile:13 DL3008 Pin versions in apt get install. Instead of `apt-get install <package>` use `apt-get install <package>=<version>`
./php-apache/7.2/Dockerfile:24 SC2028 echo may not expand escape sequences. Use printf.
./php-apache/5.6/Dockerfile:6 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
./php-apache/5.6/Dockerfile:7 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
./php-apache/5.6/Dockerfile:13 DL3008 Pin versions in apt get install. Instead of `apt-get install <package>` use `apt-get install <package>=<version>`
./php-apache/5.6/Dockerfile:24 SC2028 echo may not expand escape sequences. Use printf.
./php-apache-shell/base/Dockerfile:5 DL3008 Pin versions in apt get install. Instead of `apt-get install <package>` use `apt-get install <package>=<version>`
./php-apache-shell/7.2/Dockerfile:5 DL3008 Pin versions in apt get install. Instead of `apt-get install <package>` use `apt-get install <package>=<version>`
./php-apache-shell/5.6/Dockerfile:5 DL3008 Pin versions in apt get install. Instead of `apt-get install <package>` use `apt-get install <package>=<version>`

I do not think that we want to make all changes immediately. However, we can review rules, select which apply to facilitate future maintenance (as any tests), especially after transferring the task to fresh person.

[gregorybrzeski]

Why hadolint ?

[ad-m]

This - in my opinion - is the linter with the largest community. I am open to other suggestions.

[gregorybrzeski]

Is the largest community the most important factor to take into account in here ? any other angels ? I am not against, I just want to understand why hadolint and not something else.