ref(scheduler): introduce a build pod template function to reduce duplication in scheduling code

ReplicationController can take a fully formed Pod Template (include Kind / apiVerison) within its spec/template section

This allows reuse of the Pod Template between deis run and RCs (and Deployments in the future).

The distinction between buildpack and "the rest" templates was eliminated by moving more of the env var and volume logic into the build pod template and set container functions

Author: helgi