Use only s2i for building the website

[mscherer]

Since we are moving to openshift v3 and s2i, we should make sure the website is using only 1 single way to be built.

I propose that we drop the dockerfile and related things to build, and also the atomicapp. So we can build using s2i and then give instruction on how to run the generated container. This would permit to close a few bugs.