Add CentOS based images for 2.0

[tmds]

Implements #36

[tmds]

I've included the following in the Jenkins pr-checker config:

# Build and test CentOS images
TEST_OPENSHIFT=false BUILD_CENTOS=true ./build.sh

[jerboaa]

This looks good to me. Nice work!

As a follow-up we might want to create a CentOS mirror of this too:
https://github.com/redhat-developer/dotnet-jenkins-slave

[jerboaa]

Then we could also add a mirror of the image stream and the templates should work with centos versions too.

[aslicerh]

Can we name the new Dockerfile to something like Dockerfile.centos? That would keep the naming convention consistent, and it would get in the way less for the container builds, where we currently sym link Dockerfile.rhel7 to Dockerfile.

[tmds]

Can we name the new Dockerfile to something like Dockerfile.centos?

I named this Dockerfile since it seems to be the naming convention for CentOS in the other s2i repos (e.g. nodejs, python).

@jerboaa wdyt?

[jerboaa]

Can we name the new Dockerfile to something like Dockerfile.centos?

What @tmds said. The convention is Dockerfile being the centos version upstream. Dockerfile.rhel7 being the RHEL-based version. We should stick with that convention as it will make something like this work out-of-the-box on OpenShift:

 $ oc new-build --strategy=docker --context-dir=2.0/runtime https://github.com/redhat-developer/s2i-dotnetcore

[aslicerh]

Ah, ok, request withdrawn then, and no complains from my side.

[tmds]

Thank you for review @jerboaa @aslicerh!