Add docker containers

This adds information to the containers that are in Docker Hub that work both with MATLAB and Octave. I decided to take the easy way out by building the containers on top of the official MATLAB containers to make maintenance and reliability as smooth as possible. It is just a Dockerfile which builds Dynare from source. The MATLAB test suite runs through in the containers. I also tested the example mod files with Octave. Let's see whether the images are actually used and later decide if we want to rebase it on Debian and use the packages of Dynare.