[do not merge] Compile an sh build script

This is an experiment and not meant to be merged, yet. Still sending a pull request to notify everybody :)

This changes travis-build to compile a shell script from the directives given in the various language builders. The eventual goal is to get rid of the need of a persistent ssh session. Instead we'd just pass a single build script and tail a build log.

Since we're doing a fair amount of logic in travis-build (such as checking for exit codes, timeouts etc) all this has to happen within the shell script now.

To make this work i've added a rather simplistic dsl to describe shell scripts the way we need.

The code on this branch currently does not take care of anything but compiling the scripts.