Work towards a state-less server

Currently the landing server is treated as a virtual machine. The container image should never be deleted, otherwise all the modifications on the server are lost. The is clearly in contrast to dockers philosophy of ephemeral and state-less containers. The goal of this issue is to reduce the state dependence of the landing server. There are two initiatives to achieve this goal.

1. Add a script which is executed when the image is built. The server administrator should install all required tools. If new tools are required, they should be added to the install script and the image should be rebuilt. It is unlikely that this separate file gives rise to merge conflicts in git when pulling new versions.

2. The home directories should be mounted in the container to make user data persistent. It has to be decided, whether this should be the host systems home directory or a separate one.