make helmValues work in non init-chart workflows

[dexhorthy]

What I Did

I made HelmValues work in non init-chart workflows.

full POC (also in integration test):

---
assets:
  v1: []

config: {}

lifecycle:
  v1:
    - render:
        root: ./
        assets:
          v1:
            - github:
                dest: ./installer/consul
                repo: helm/charts
                path: stable/consul
                ref: master
                strip_path: true
    - helmValues:
        path: installer/consul/values.yaml
    - render:
        root: ./
        assets:
          v1:
            - helm:
                dest: ./installer/base
                local:
                  chart_root: ./installer/consul
                values_from:
                  # haaaack, helmValues still needs a configurable dest path for us to store the output
                  path: .ship/tmp
    - kustomize:
        base: installer/base
        dest: installer/consul-rendered.yaml

How I Did it

• add path field to daemontypes.Step.HelmValues, copy it over from existing api.Step.HelmValues
• read this HelmValues.Path field in GET /navcycle/step/helm-values and the POST /helm-values, falling back to the old way of .ship/tmp/values.yaml
• When linting chart, use filepath.Dir(step.HelmValues.path) as the base directory for linting, defaulting to the old .ship/tmp/chart
• tried to remove constants/global-state-in-the-filesystem where possible

How to verify it

• ship init the ship.yml in integration/base/shipapp-helm-values/input/.ship/ship.yaml
• touched some newer unfork code that I'm not as familiar with--still need to test unfork

Description for the Changelog

Make some changes around path handling that allow a lifecycle.v1.helmValues step to be used outside of the core ship init <chart> workflow.

[dexhorthy]

I don't know what's going on with Circle but the test build finished here https://circleci.com/gh/dexhorthy/ship/2115?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link, for some reason it got a different name.