self contained docker image building pspp from source

[Oren Ish-Shalom]

Hi all,
In case someone needs a `without-gui` build from source,
controlling various steps of the build / compilation flags etc.,
Take a look at this psppdocker GitHub Dockerfile
<https://github.com/OrenGitHub/psppdocker>.

* Hope I didn't reinvent the wheel by missing a similar thing