Helm: allow relative paths for helm charts in watches.yaml file

[joelanford]

Description of the change:

• Changes the Helm operator to support relative paths to chart directories in the watches.yaml file. If a relative paths is found, a base path will be prepended. The prefered base path comes from the HELM_CHARTS_PATH environment variable. If that is empty or not set, the operator falls back to the HOME directory, which maintains backward compatibility with existing projects.
• Updates the Helm operator project's watches.yaml scaffold to use a relative path instead of an absolute path.

Motivation for the change:
Allowing relative paths simplifies the experience of switching between operator-sdk up local and running in-cluster.

Now local filesystem changes do not have to be made for up local to work. Previously, developers had to copy their chart to /opt/helm/helm-charts/<chart-name>, create a symlink, or change their watches.yaml temporarily to point to the absolute path of their local project (and then be forced to change it back before running operator-sdk build)

[camilamacedo86]

Looking

I would like to test locally first.

[estroz]

/lgtm

[camilamacedo86]

.

[camilamacedo86]

/lgtm /approved