All scripts and Dockerfiles should use same variables

[Smiley73]

Currently we have variables defined in many different places (e.g. kubectl version). We need to make sure we're consistent and pull it all from the same sources. Maybe travis.yml is the right place?

What happens?

If we change a version, we have to change it in many places and most likely will forget one.

What were you expecting to happen?

Changing a version is a simple task in one file.

[etsauer]

@Smiley73 can you provide some examples?

[Smiley73]

Just some random examples. I'm sure there are more...

https://github.com/KohlsTechnology/eunomia/blob/master/scripts/build-images.sh#L19
https://github.com/KohlsTechnology/eunomia/blob/master/scripts/images-pull-push.sh#L21
https://github.com/KohlsTechnology/eunomia/blob/master/template-processors/base/Dockerfile#L6
https://github.com/KohlsTechnology/eunomia/blob/master/template-processors/helm/Dockerfile#L4

The kubectl version for example should be consistent across all our scripts.

[seanmalloy]

The release version variables will get cleaned up as part of #64. I think the scripts/images-pull-push.sh script can probably be removed. I don't think we need this.