Create Docker image with ready-to-use development environment

[dboehmer]

Good example of software project: https://github.com/roschaefer/rundfunk-mitbestimmen#installation-and-usage-with-docker-quick-but-without-software-tests

A interested developer/potential contributor should be able to easily call Docker to obtain a dev environment without any Perl, Coocook or sysadmin knowledge.

[dboehmer]

@ChristinaSi asked me what this should include:

• if possible system Perl (preinstalled on allmost all Linux distros like in Ubuntu) or (fallback or maybe even better) most recent stable Perl version (5.26.1 as of March 2018) installed with Perlbrew
• CPAN-Minus cpanm program
• all necessary CPAN modules for Coocook like described in README.md
• a Git checkout of the Coocook repository
• a SQLite database deployed with the DB schema [future: maybe a PostgreSQL server once we started using PostgreSQL?]

Of course, I can help with any of the Perl-related stuff.

Acceptance criteria:

• one can easily retrieve the Coocook Docker image and run it
• the Coocook web interface is easily accessible, e.g. at http://localhost:3000/, via browser on the host OS
• changes can be made to the Coocook code (with some editor on the container OS or even better with any editor on the host OS)
• changes can be committed and pushed with Git on the host or container OS
• the SQLite database can be manipulated with sqlite3 on the host or container OS

[dboehmer]

I'd prefer to install Coocook in /opt/coocook/.