Develop checklist for build Conveyor release for multiple Elastic releases

[milutz]

As a core developer, I need a process such that I can accurately and repeatedly create multiple different intestances of a given release of Conveyor, such that they are configured for different versions of the Elastic stack

Goal of this issue is just to create the steps that you would replete to build multiple Elastic stack version - a likely future goal would be to build automation to do that. To prepare for the future goal we want to collect information about any automation short-cuts - specifically interested in information on the ELK built in version setting functionality that @malave though he saw.

[milutz]

Talked to @malave and he pointed at these docs for the functionality thats built into kibana: https://github.com/elastic/kibana-plugin-helpers/blob/master/README.md#settings-for-build

[wrathagom]

Work in progress here https://github.com/samtecspg/conveyor/blob/master/docs/_developer_docs/new-build-version.md

[milutz]

A (rough) process for this has been created, but not quite ready to be checklistized here.

The first section of the readme in https://github.com/samtecspg/kibana-plugin-build (described as "day two") has a process for building as it stands now.

Seems like it should be refined one more pass before closing this.